Manual of Surgery/Chapter XXI

CHAPTER XXI

DISEASES OF JOINTS

Definition of terms--Ankylosis. DISEASES: Errors of

   development--Bacterial diseases: _Pyogenic_; _Gonorrhoeal_;
   _Tuberculous_; _Syphilitic_; _Acute rheumatism_--Diseases
   associated with certain constitutional conditions: _Gout_; _Chronic
   articular rheumatism_; _Arthritis deformans_;
   _Haemophilia_--Diseases associated with affections of the nervous
   system: _Neuro-arthropathies_; _Charcot's disease_--Hysterical or
   mimetic affections of joints--Tumours and cysts--Loose bodies.

1. Definition of Terms.#--The term _synovitis_ is applied to any reaction

which affects the synovial membrane of a joint. It is usually associated with effusion of fluid, and this may be serous, sero-fibrinous, or purulent. As the term synovitis merely refers to the tissue involved, it should always be used with an adjective--such as gouty, gonorrhoeal, or tuberculous--which indicates its pathological nature.

The terms _hydrops_, _hydrarthrosis_, and _chronic serous synovitis_ are synonymous, and are employed when a serous effusion into the joint is the prominent clinical feature. Hydrops may occur apart from disease--for example, in the knee-joint from repeated sprains, or when there is a loose body in the joint--but is met with chiefly in the chronic forms of synovitis which result from gonorrhoea, tuberculosis, syphilis, arthritis deformans, or arthropathies of nerve origin.

_Arthritis_ is the term applied when not only the synovial membrane but the articular surfaces, and it may be also the ends of the bones, are involved, and it is necessary to prefix a qualifying adjective which indicates its nature. When effusion is present, it may be serous, as in arthritis deformans, or sero-fibrinous or purulent, as in certain forms of pyogenic and tuberculous arthritis. Wasting of the muscles, especially the extensors, in the vicinity of the joint is a constant accompaniment of arthritis. On account of the involvement of the articular surfaces, arthritis is apt to be followed by ankylosis.

The term _empyema_ is sometimes employed to indicate that the cavity of the joint contains pus. This is observed chiefly in chronic disease of pyogenic or tuberculous origin, and is usually attended with the formation of abscesses outside the joint.

_Ulceration of cartilage_ and _caries of the articular surfaces_ are common accompaniments of the more serious and progressive forms of joint disease, especially those of bacterial origin. The destruction of cartilage may be secondary to disease of the synovial membrane or of the subjacent bone. When the disease begins as a synovitis, the synovial membrane spreads over the articular surface, fuses with the cartilage and eats into it, causing defects or holes which are spoken of as ulcers. When the disease begins in the bone, the marrow is converted into granulation tissue, which eats into the cartilage and separates it from the bone. Following on the destruction of the cartilage, the articular surface of the bone undergoes disintegration, a condition spoken of as _caries of the articular surface_. The occurrence of ulceration of cartilage and of articular caries is attended with the clinical signs of fixation of the joint from involuntary muscular contraction, wasting of muscles, and starting pains. These _starting pains_ are the result of sudden involuntary movements of the joint. They occur most frequently as the patient is dropping off to sleep; the muscles becoming relaxed, the sensitive ulcerated surfaces jar on one another, which causes sudden reflex contraction of the muscles, and the resulting movement being attended with severe pain, wakens the patient with a start. Advanced articular caries is usually associated with some abnormal attitude and with shortening of the limb. It may be possible to feel the bony surfaces grate upon one another. When all its constituent elements are damaged or destroyed, a joint is said to be _disorganised_. Should recovery take place, repair is usually attended with union of the opposing articular surfaces either by fibrous tissue or by bone.

1. Conditions of Impaired Mobility of Joints.#--There are four conditions

of impaired mobility in joints: rigidity, contracture, ankylosis, and locking. _Rigidity_ is the fixation of a joint by involuntary contraction of muscles, and is of value as a sign of disease in deep-seated joints, such as the hip. It disappears under anaesthesia.

_Contracture_ is the term applied when the fixation is due to permanent shortening of the soft parts around a joint--muscles, tendons, ligaments, fasciae, or skin. As the structures on the flexor aspect are more liable to undergo such shortening, contracture is nearly always associated with flexion. Contracture may result from disease of the joint, or from conditions outside it--for example, disease in one of the adjacent bones, or lesions of the nerves.

_Ankylosis_ is the term applied when impaired mobility results from changes involving the articular surfaces. It is frequently combined with contracture. Three anatomical varieties of ankylosis are recognised--(a) The _fibrous_, in which there are adhesions between the opposing surfaces, which may be in the form of loose isolated bands of fibrous tissue, or may bind the bones so closely together as to obliterate the cavity of the joint. The resulting stiffness, therefore, varies from a mere restriction of the normal range of movement, up to a close union of the bones which prevents movement. Fibrous ankylosis may follow upon injury, especially dislocation or fracture implicating a joint, or it may result from any form of arthritis. (b) _Cartilaginous ankylosis_ implies the fusion of two apposed cartilaginous surfaces. It is often found between the patella and the trochlear surface of the femur in tuberculous disease of the knee. The fusion of the cartilaginous surfaces is preceded by the spreading of a vascular connective tissue, derived from the synovial membrane, over the articular cartilage. Clinically, it is associated with absolute immobility, (c) _Bony ankylosis_ or _synostosis_ is an osseous union between articulating surfaces (Figs. 154 and 155). It may follow upon fibrous or cartilaginous ankylosis, or may result from the fusion of two articular surfaces which have lost their cartilage and become covered with granulations. In the majority of cases it is to be regarded as a reparative process, presenting analogies with the union of fracture.

[Illustration: FIG. 154.--Osseous Ankylosis of Femur and Tibia in position of flexion.]

The term _arthritis ossificans_ has been applied by Joseph Griffiths to a condition in which the articular surfaces become fused without evident cause.

The occurrence of ankylosis in a joint before the skeleton has attained maturity does not appear to impair the growth in length of the bones affected; ankylosis of the temporo-maxillary joints, however, greatly impairs the growth of the mandible. When there is arrest of growth accompanying ankylosis, it usually depends on changes in the ossifying junctions caused by the original disease.

To differentiate by manipulation between muscular fixation and ankylosis, it may be necessary to anaesthetise the patient. The nature and extent of ankylosis may be learned by skiagraphy; in osseous ankylosis the shadow of the two bones is a continuous one. In fibrous as contrasted with osseous ankylosis mobility may be elicited, although only to a limited extent; while in osseous ankylosis the joint is rigidly fixed, and attempts to move it are painless.

[Illustration: FIG. 155.--Osseous Ankylosis of Knee in the flexed position following upon Tuberculous Arthritis.

(Anatomical Museum, University of Edinburgh.)]

The _treatment_ is influenced by the nature of the original lesion, the variety of the ankylosis, and the attitude of the joint. When there is restriction of movement due to fibrous adhesions, these may be elongated or ruptured. Elongation of the adhesions may be effected by manipulations, exercises, and the use of special forms of apparatus--such as the application of weights to the limb. It may be necessary to administer an anaesthetic before rupturing strong fibrous adhesions, and this procedure must be carried out with caution, in view of such risks as fracture of the bone--which is often rarefied--or separation of an epiphysis. There is also the risk of fat embolism, and of re-starting the original disease. The giving way of adhesions may be attended with an audible crack; and the procedure is often followed by considerable pain and effusion into the joint, which necessitate rest for some days before exercises and manipulations can be resumed.

_Operative treatment_ may be called for in cases in which the bones are closely bound to one another by fibrous or by osseous tissue.

_Arthrolysis_, which consists in opening the joint and dividing the fibrous adhesions, is almost inevitably followed by their reunion.

_Arthroplasty._--Murphy of Chicago devised this operation for restoring movement to an ankylosed joint. It consists in transplanting between the bones a flap of fat-bearing tissue, from which a bursal cavity lined with endothelium and containing a fluid rich in mucin is ultimately formed.

Arthroplasty is most successful in ankylosis following upon injury; when the ankylosis results from some infective condition such as tuberculosis or gonorrhoea, it is liable to result in failure either because of a fresh outbreak of the infection or because the ankylosis recurs.

When arthroplasty is impracticable, and a movable joint is desired--for example at the elbow--a considerable amount of bone, and it may be also of periosteum and capsular ligament, is resected to allow of the formation of a false joint.

When bony ankylosis has occurred with the joint in an undesirable attitude--for example flexion at the hip or knee--it can sometimes be remedied by osteotomy or by a wedge-shaped resection of the bone, with or without such additional division of the contracted soft parts as will permit of the limb being placed in the attitude desired.

Bony ankylosis of the joints of a finger, whether the result of injury or disease, is difficult to remedy by any operative procedure, for while it is possible to restore mobility, the new joint is apt to be flail-like.

_Locking._--A joint is said to lock when its movements are abruptly arrested by the coming together of bony outgrowths around the joint. It is best illustrated in arthritis deformans of the hip in which new bone formed round the rim of the acetabulum mechanically arrests the excursions of the head of the femur. The new bone, which limits the movements, is readily demonstrated in skiagrams; it may be removed by operative means. Locking of joints is more often met with as a result of injuries, especially in fractures occurring in the region of the elbow. In certain injuries of the semilunar menisci of the knee, also, the joint is liable to a variety of locking, which differs, however, in many respects from that described above.

1. Errors of Development.#--These include congenital dislocations and

other deformities of intra-uterine origin, such as abnormal laxity of joints, absence, displacement, or defective growth of one or other of the essential constituents of a joint. The more important of these are described along with the surgery of the Extremities.

DISEASES OF JOINTS

1. Bacterial Diseases.#--In most bacterial diseases the organisms are

carried to the joint in the blood-stream, and they lodge either in the synovial membrane or in one of the bones, whence the disease subsequently spreads to the other structures of the joint. Organisms may also be introduced through accidental wounds. It has been shown experimentally that joints are among the most susceptible parts of the body to infection, and this would appear to be due to the viscid character of the synovial fluid, which protects organisms from bactericidal agents in the tissues and fluids.

PYOGENIC DISEASES

The commoner pyogenic diseases are the result of infection of one or other of the joint structures with _staphylococci_ or _streptococci_, which may be demonstrated in the exudate in the joint and in the substance of the synovial membrane. The mode of infection is the same as in the pyogenic diseases of bone, the metastasis occurring most frequently from the mucous membrane of the pharynx (J. B. Murphy). The localisation of the infection in a particular joint is determined by injury, exposure to cold, antecedent disease of the joint, or other factors, the nature of which is not always apparent.

The effects on the joint vary in severity. In the milder forms, there is engorgement and infiltration of the synovial membrane, and an effusion into the cavity of the joint of serous fluid mixed with flakes of fibrin--_serous synovitis_. In more severe infections the exudate consists of pus mixed with fibrin, and, it may be, red blood corpuscles--_purulent_ or _suppurative synovitis_; the synovial membrane and the ligaments are softened, and the surface of the membrane presents granulations resembling those on an ulcer; foci of suppuration may develop in the peri-articular cellular tissue and result in abscesses. In _acute arthritis_, all the structures of the joint are involved; the articular cartilage is invaded by granulation tissue derived from the synovial membrane, and from the marrow of the subjacent bone; it presents a worm-eaten or ulcerated appearance, or it may undergo necrosis and separate, exposing the subjacent bone and leading to disintegration of the osseous trabeculae--_caries_. With the destruction of the ligaments, the stability of the joint is lost, and it becomes disorganised.

The _clinical features_ vary with the extent of the infection. When this is confined to the synovial and peri-synovial tissues--_acute serous_ and _purulent synovitis_--there is the usual general reaction, associated with pyrexia and great pain in the joint. The part is hot and swollen, the swelling assuming the shape of the distended synovial sac, fluctuation can usually be elicited, and the joint is held in the flexed position.

When the joint is infected by extension from the surrounding cellular tissue, the joint lesion may not be recognised at an early stage because of the swollen condition of the limb, and because there are already symptoms of toxaemia. We have observed a case in which both the hip and knee joints were infected from the cellular tissue.

If the infection involves all the joint structures--_acute arthritis_--the general and local phenomena are intensified, the temperature rises quickly, often with a rigor, and remains high; the patient looks ill, and is either unable to sleep or the sleep is disturbed by starting pains. The joint is held rigid in the flexed position, and the least attempt at movement causes severe pain; the slightest jar--even the shaking of the bed--may cause agony. The joint is hot, tensely distended, and there may be oedema of the peri-articular tissues or of the limb as a whole. If the pus perforates the joint capsule, there are signs of abscess or of diffuse suppuration in the cellular tissue. The final disorganisation of the joint is indicated by abnormal mobility and grating of the articular surfaces, or by spontaneous displacement of the bones, and this may amount to dislocation. In the acute arthritis of infants, the epiphysis concerned may be separated and displaced.

When the _joint is infected through an external wound_, the anatomical features are similar to those observed when the infection has reached the joint by the blood-stream, but the destructive changes tend to be more severe and are more likely to result in disorganisation.

The _terminations_ vary with the gravity of the infection and with the stage at which treatment is instituted. In the milder forms recovery is the rule, with more or less complete restoration of function. In more severe forms the joint may be permanently damaged as a result of fibrous or bony ankylosis, or from displacement or dislocation. From changes in the peri-articular structures there may be contracture in an undesirable position, and in young subjects the growth of the limb may be interfered with. The persistence of sinuses is usually due to disease in one or other of the adjacent bones. In the most severe forms, and especially when several joints are involved, death may result from toxaemia.

The _treatment_ is carried out on the same principles as in other pyogenic infections. The limb is immobilised in such an attitude that should stiffness occur there will be the least interference with function. Extension by weight and pulley is the most valuable means of allaying muscular spasm and relieving intra-articular tension and of counteracting the tendency to flexion; as much as 15 or 20 pounds may be required to relieve the pain.

The induction of hyperaemia is sometimes remarkably efficacious in relieving pain and in arresting the progress of the infection. If the fluid in the joint is in sufficient quantity to cause tension, if it persists, or if there is reason to suspect that it is purulent, it should be withdrawn without delay; an exploring syringe usually suffices, the skin being punctured with a tenotomy knife, and, as practised by Murphy, 5 to 15 c.c. of a 2 per cent. solution of formalin in glycerin are injected and the wound is closed. In virulent infections the injection may be repeated in twenty-four hours. Drainage by tube or otherwise is to be condemned (Murphy). A vaccine may be prepared from the fluid in the joint and injected into the subcutaneous cellular tissue.

Suppuration in the peri-articular soft parts or in one of the adjacent bones must be looked for and dealt with.

When convalescence is established, attention is directed to the restoration of the functions of the limb, and to the prevention of stiffness and deformity by movements and massage, and the use of hot-air and other baths.

At a later stage, and especially in neglected cases, operative and other measures may be required for deformity or ankylosis.

1. Metastatic Forms of Pyogenic Infection#

In #pyaemia#, one or more joints may fill with pus without marked symptoms or signs, and if the pus is aspirated without delay the joint often recovers without impairment of function.

In #typhoid fever#, joint lesions result from infection with the typhoid bacillus alone or along with pyogenic organisms, and run their course with or without suppuration; there is again a remarkable absence of symptoms, and attention may only be called to the condition by the occurrence of dislocation.

Joint lesions are comparatively common in #scarlet fever#, and were formerly described as scarlatinal rheumatism. The most frequent clinical type is that of a serous synovitis, occurring within a week or ten days from the onset of the fever. Its favourite seat is in the hand and wrist, the sheaths of the extensor tendons as well as the synovial membrane of the joints being involved. It does not tend to migrate to other joints, and rarely lasts longer than a few days. It is probably due to the specific virus of scarlet fever.

At a later stage, especially in children and in cases in which the throat lesion is severe, an arthritis is sometimes observed that is believed to be a metastasis from the throat; it may be acute and suppurative, affect several joints, and exhibit a septicaemic or pyaemic character.

The joints of the lower extremity are especially apt to suffer; the child is seriously ill, is delirious at night, develops bed-sores over the sacrum and, it may happen that, not being expected to recover, the legs are allowed to assume contracture deformities with ankylosis or dislocation at the hip and flexion ankylosis at the knees; should the child survive, the degree of crippling may be pitiable in the extreme; prolonged orthopaedic treatment and a series of operations--arthroplasty, osteotomies, and resections--may be required to restore even a limited capacity of locomotion.

1. Pneumococcal affections of joints#, the result of infection with the

pneumococcus of Fraenkel, are being met with in increasing numbers. The local lesion varies from a _synovitis_ with infiltration of the synovial membrane and effusion of serum or pus, to an _acute arthritis_ with erosion of cartilage, caries of the articular surfaces, and disorganisation of the joint. The knee is most frequently affected, but several joints may suffer at the same time. In most cases the joint affection makes its appearance a few days after the commencement of a pneumonia, but in a number of instances, especially among children, the lung is not specially involved, and the condition is an indication of a generalised pneumococcal infection, which may manifest itself by endocarditis, empyema, meningitis, or peritonitis, and frequently has a fatal termination. The differential diagnosis from other forms of pyogenic infection is established by bacteriological examination of the fluid withdrawn from the joint. The treatment is carried out on the same lines as in other pyogenic infections, considerable reliance being placed on the use of autogenous vaccines.

In #measles#, #diphtheria#, #smallpox#, #influenza#, and #dysentery#, similar joint lesions may occur.

The joint lesions which accompany #acute rheumatism# or "rheumatic fever" are believed to be due to a diplococcus. In the course of a general illness in which there is moderate pyrexia and profuse sweating, some of the larger joints, and not infrequently the smaller ones also, become swollen and extremely sensitive, so that the sufferer lies in bed helpless, dreading the slightest movement. From day to day fresh joints are attacked, while those first affected subside, often with great rapidity. Affections of the heart-valves and of the pericardium are commonly present. On recovery from the acute illness, it may be found that the joints have entirely recovered, but in a small proportion of cases certain of them remain stiff and pass into the crippled condition described under chronic rheumatism. There is no call for operative interference.

1. Gonococcal Affections of Joints.#--These include all forms of joint

lesion occurring in association with gonorrhoeal urethritis, vulvo-vaginitis, or gonorrhoeal ophthalmia. They may develop at any stage of the urethritis, but are most frequently met with from the eighteenth to the twenty-second day after the primary infection, when the organisms have reached the posterior urethra; they have been observed, however, after the discharge has ceased. There is no connection between the severity of the gonorrhoea and the incidence of joint disease. In women, the gonorrhoeal nature of the discharge must be established by bacteriological examination.

As a complication of ophthalmia, the joint lesions are met with in infants, and occur more commonly towards the end of the second or during the third week.

The gonococcus is carried to the joint in the blood-stream and is first deposited in the synovial membrane, in the tissues of which it can usually be found; it may be impossible to find it in the exudate within the joint. The joint lesions may be the only evidence of metastasis, or they may be part of a general infection involving the endocardium, pleura, and tendon sheaths.

The joints most frequently affected are the knee, elbow, ankle, wrist, and fingers. Usually two or more joints are affected.

Several clinical types are differentiated. (1) A _dry poly-arthritis_ met with in the joints and tendon sheaths of the wrist and hand, formerly described as gonorrhoeal rheumatism, which in some cases is trifling and evanescent, and in others is persistent and progressive, and results in stiffness of the affected joints and permanent crippling of the hand and fingers.

(2) The commonest type is a _chronic synovitis_ or _hydrops_, in which the joint--very often the knee--becomes filled with a serous or sero-fibrinous exudate. There are no reactive changes in the synovial membrane, cellular tissue, or skin, nor is there any fever or disturbance of health. The movements are free except in so far as they are restricted by the amount of fluid in the joint. It usually subsides in two or three weeks under rest, but tends to relapse.

(3) An _acute synovitis_ with peri-articular phlegmon is most often met with in the elbow, but it occurs also in the knee and ankle. There is a sudden onset of severe pain and swelling in and around the joint, with considerable fever and disturbance of health. The slightest movement causes pain, and the part is sensitive to touch. The skin is hot and tense, and in the case of the elbow may be red and fiery as in erysipelas.

The deposit of fibrin on the synovial membrane and on the articular surfaces may lead to the formation of adhesions, sometimes in the form of isolated bands, sometimes in the form of a close fibrous union between the bones.

(4) A _suppurative arthritis_, like that caused by ordinary pus microbes, may be the result of gonococcal infection alone or of a mixed infection. Usually only one joint is affected, but the condition may be multiple. The articular cartilages are destroyed, the ends of the bones are covered with granulations, extra-articular abscesses form, and complete osseous ankylosis results.

The _diagnosis_ is often missed because the possibility of gonorrhoea is not suspected.

The denial of the disease by the patient is not always to be relied upon, especially in the case of women, as they may be ignorant of its presence. The chief points in the differential diagnosis from acute articular rheumatism are, that the gonorrhoeal affection is more often confined to one or two joints, has little tendency to wander from joint to joint, and its progress is not appreciably influenced by salicylates, although these drugs may relieve pain. The conclusive point is the recognition of a gonorrhoeal discharge or of threads in the urine.

The disease may persist or may relapse, and the patient may be laid up for weeks or months, and may finally be crippled in one or in several joints.

The _treatment_--besides that of the urethral disease or of the ophthalmia--consists in rest until all pain and sensitiveness have disappeared. The pain is relieved by salicylates, but most benefit follows weight extension, the induction of hyperaemia by the rubber bandage and hot-air baths; if the joint is greatly distended, the fluid may be withdrawn by a needle and syringe. Detoxicated vaccines should be given from the first, and in afebrile cases the injection of a foreign protein, such as anti-typhoid vaccine, is beneficial (Harrison).

Murphy has found benefit from the introduction into the joint, in the early stages, of from 5 to 15 c.c. of a 2 per cent. solution of formalin in glycerin. This may be repeated within a week, the patient being kept in bed with light weight extension. In the chronic hydrops the fluid is withdrawn, and about an ounce of a 1 per cent. solution of protargol injected; the patient should be warned of the marked reaction which follows.

After all symptoms have settled down, but not till then, for fear of exciting relapse or metastasis, the joint is massaged and exercised. Stiffness from adhesions is most intractable, and may, in spite of every attention, terminate in ankylosis even in cases where there has been no suppuration. Forcible breaking down of adhesions under anaesthesia is not recommended, as it is followed by great suffering and the adhesions re-form. Operation for ankylosis--arthroplasty--should not be undertaken, as the ankylosis recurs.

TUBERCULOUS DISEASE

Tuberculous disease of joints results from bacillary infection through the arteries. The disease may commence in the synovial membrane or in the marrow of one of the adjacent bones, and the relative frequency of these two seats of infection has been the subject of considerable difference of opinion. The traditional view of Konig is that in the knee and most of the larger joints the disease arises in the bone and in the synovial membrane in about equal proportion, and that in the hip the number of cases beginning in the bones is about five times greater than that originating in the membrane. This estimate, so far as the actual frequency of bone lesions is concerned, has been generally accepted, but recent observers, notably John Fraser, do not accept the presence of bone lesions as necessarily proving that the disease commenced in the bones; he maintains, and we think with good grounds, that in many cases the disease having commenced in the synovial membrane, slowly spreads to the bone by way of the blood vessels and lymphatics, and gives rise to lesions in the marrow.

1. Morbid Anatomy.#--Tuberculous disease in the articular end of a long

bone may give rise to _reactive changes_ in the adjacent joint, characterised by effusion and by the extension of the synovial membrane over the articular surfaces. This may result in the formation of adhesions which obliterate the cavity of the joint or divide it into compartments. These lesions are comparatively common, and are not necessarily due to actual tuberculous infection of the joint.

The _infection of the joint_ by tubercle originating in the adjacent bone may take place at the periphery, the osseous focus reaching the surface of the bone at the site of reflection of the synovial membrane, and the infection which begins at this point then spreads to the rest of the membrane. Or it may take place in the central area, by the projection of tuberculous granulation tissue into the joint following upon erosion of the cartilage (Fig. 156).

[Illustration: FIG. 156.--Section of Upper End of Fibula, showing caseating focus in marrow, erupting on articular surface and infecting joint.]

_Changes in the Synovial Membrane._--In the majority of cases there is a _diffuse thickening of the synovial membrane_, due to the formation of granulation tissue, or of young connective tissue, in its substance. This new tissue is arranged in two layers--the outer composed of fully formed connective or fibrous tissue, the inner of embryonic tissue, usually permeated with miliary tubercles. On opening the joint, these tubercles may be seen on the surface of the membrane, or the surface may be covered with a layer of fibrinous or caseating tissue. Where there is greater resistance on the part of the tissues, there is active formation of young connective tissue which circumscribes or encapsulates the tubercles, so that they remain embedded in the substance of the membrane, and are only seen on cutting into it.

The thickened synovial membrane is projected into the cavity of the joint, filling up its pouches and recesses, and spreading over the surface of the articular cartilage "like ivy growing on a wall." Wherever the synovial tissue covers the cartilage it becomes adherent to and fused with it. The morbid process may be arrested at this stage, and fibrous adhesions form between the opposing articular surfaces, or it may progress, in which case further changes occur, resulting in destruction of the articular cartilage and exposure of the subjacent bone.

In rare instances the synovial membrane presents nodular masses or lumps, resembling the tuberculous tumours met with in the brain; they project into the cavity of the joint, are often pedunculated, and may give rise to the symptoms of loose body. The fringes of synovial membrane may also undergo a remarkable development, like that observed in arthritis deformans, and described as arborescent lipoma. Both these types are almost exclusively met with in the knee.

_The Contents of Tuberculous Joints._--In a large proportion of cases of synovial tuberculosis the joint is entirely filled up by the diffuse thickening of the synovial membrane. In a small number there is an abundant serous exudate, and with this there may be a considerable formation of fibrin, covering the surface of the membrane and floating in the fluid as flakes or masses; under the influence of movement it may assume the shape of melon-seed bodies. More rarely the joint contains pus, and the surface of the synovial membrane resembles the wall of a cold abscess.

_Ulceration and Necrosis of Cartilage._--The synovial tissue covering the cartilage causes pitting and perforation of the cartilage and makes its way through it, and often spreads widely between it and the subjacent bone; the cartilage may be detached in portions of considerable size. It may be similarly ulcerated or detached as a result of disease in the bone.

_Caries of Articular Surfaces._--Tuberculous infiltration of the marrow in the surface cancelli breaks up the spongy framework of the bone into minute irregular fragments, so that it disintegrates or crumbles away--caries. When there is an absence of caseation and suppuration, the condition is called _caries sicca_.

The pressure of the articular surfaces against one another favours the progress of ulceration of cartilage and of articular caries. These processes are usually more advanced in the areas most exposed to pressure--for example, in the hip-joint, on the superior aspect of the head of the femur, and on the posterior and upper segment of the acetabulum.

The occurrence of _pathological dislocation_ is due to softening and stretching of the ligaments which normally retain the bones in position, and to some factor causing displacement, which may be the accumulation of fluid or of granulations in the joint, the involuntary contraction of muscles, or some movement or twist of the limb. The occurrence of dislocation is also favoured by destructive changes in the bones.

_Peri-articular tubercle and abscess_ may result from the spread of disease from the bone or joint into the surrounding tissues, either directly or by way of the lymphatics. A peri-articular abscess may spread in several directions, sometimes invading tendon sheaths or bursae, and finally reaching the skin surface by tortuous sinuses.

Reactive changes in the vicinity of tuberculous joints are of common occurrence, and play a considerable part in the production of what is clinically known as _white swelling_. New connective tissue forms in the peri-articular fat and between muscles and tendons. It may be tough and fibrous, or soft, vascular, and oedematous, and the peri-articular fat becomes swollen and gelatinous, constituting a layer of considerable thickness. The fat disappears and is replaced by a mucoid effusion between the fibrous bundles of connective tissue. This is what was formerly known as _gelatinous degeneration_ of the synovial membrane. In the case of the wrist the newly formed connective tissue may fix the tendons in their sheaths, interfering with the movements of the fingers. In relation to the bones also there may be reactive changes, resulting in the formation of spicules of new bone on the periosteal surfaces and at the attachment of the capsular and other ligaments; these are only met with where pyogenic infection has been superadded.

_Terminations and Sequelae._--A natural process of cure may occur at any stage, the tuberculous tissue being replaced by scar tissue. Recovery is apt to be attended with impairment of movement due to adhesions, ankylosis, or contracture of the peri-articular structures. Caseous foci in the interior of the bones may become encapsulated, and a cure be thus effected, or they may be the cause of a relapse of the disease at a later date. Interference with growth is comparatively common, and may involve only the epiphysial junctions in the immediate vicinity of the joint affected, or those of all the bones of the limb. This is well seen in adults who have suffered from severe disease of the hip in childhood--the entire limb, including the foot, being shorter and smaller than the corresponding parts of the opposite side.

Atrophic conditions are also met with, the bones undergoing fatty atrophy, so that in extreme cases they may be cut with a knife or be easily fractured. These atrophic conditions are most marked in bedridden patients, and are largely due to disuse of the limb; they are recovered from if it is able to resume its functions.

1. Clinical Features.#--These vary with the different anatomical forms of

the disease, and with the joint affected.

Sometimes the disease is ushered in by a febrile attack attended with pains in several joints--described by John Duncan as _tuberculous arthritic fever_. This is liable to be mistaken for rheumatic fever, from which, however, it differs in that there is no real migration from joint to joint; there is an absence of sweating and of cardiac complications; and no benefit follows the administration of salicylates.

In exceptional cases, tuberculous joint disease follows an acute course resembling that of the pyogenic arthritis of infants. This has been observed in children, especially in the knee, the lesion being in the synovial membrane, and attended with an accumulation of pus in the joint. If promptly treated by incision and drainage, recovery is rapid, and free movement of the joint, may be preserved.

The onset and early stages of tuberculous disease, however, are more often insidious, and are attended with so few symptoms that the disease may have obtained a considerable hold before it attracts notice. It is not uncommon for patients or their friends to attribute the condition to injury, as it often first attracts attention after some slight trauma or excessive use of the limb. The symptoms usually subside under rest, only to relapse again with use of the limb.

The initial local symptoms may be due to the presence of a focus in the neighbouring bone, perhaps causing neuralgic pains in the joint, or weakness, tiredness, stiffness, and inability to use the limb, these symptoms improving with rest and being aggravated by exertion.

It is rarely possible by external examination to recognise deep-seated osseous foci in the vicinity of joints; but if they are near the surface in a superficial bone--such as the head of the tibia--there may be local thickening of the periosteum, oedema, pain, and tenderness on pressure and on percussion.

_X-ray Appearances of Tuberculous Joints._--Gross lesions such as caseous foci in the marrow of the adjacent bone show as clear areas with an ill-defined margin; a sclerosed focus gives a denser shadow than the surrounding bone, and a sequestrum presents a dark shadow of irregular contour, and a clear interval between it and the surrounding bone.

Caries of the articular surface imparts a woolly appearance or irregular contour in place of the well-defined outline of the articular end of the bone. In bony ankylosis the shadow of the two bones is a continuous one, the joint interval having been filled up. The minor changes are best appreciated on comparison with the normal joint of the other limb.

_Wasting of muscles_ is a constant accompaniment of tuberculous joint disease. It is to be attributed partly to want of use, but chiefly to reflex interference with the trophic innervation of the muscles. It is specially well seen in the extensor and adductor muscles of the thigh in disease of the knee, and in the deltoid in disease of the shoulder. The muscles become soft and flaccid, they exhibit tremors on attempted movement, and their excitability to the faradic current is diminished. The muscular tissue may be largely replaced by fat.

_Impairment of the normal movements_ is one of the most valuable diagnostic signs, particularly in deeply seated joints such as the shoulder, hip, and spine. It is due to a protective contraction of the muscles around the joint, designed to prevent movement. This muscular fixation disappears under anaesthesia.

_Abnormal attitudes of the limb_ occur earlier, and are more pronounced in cases in which pain and other irritative symptoms of articular disease are well marked, and are best illustrated by the attitudes assumed in disease of the hip. They are due to reflex or involuntary contraction of the muscles acting on the joint, with the object of placing it in the attitude of greatest ease; they also disappear under anaesthesia. With the lapse of time they not only become exaggerated, but may become permanent from ankylosis or from contracture of the soft parts round the joint.

_Startings at night_ are to be regarded as an indication that there is progressive disease involving the articular surfaces.

_The formation of extra-articular abscess_ may take place early, or it may not occur till long after the disease has subsided. The abscess may develop so insidiously that it does not attract attention until it has attained considerable size, especially when associated with disease of the spine, pelvis, or hip. The position of the abscess in relation to different joints is fairly constant and is determined by the anatomical relationships of the capsule and synovial membrane to the surrounding tissues. The bursae and tendon sheaths in the vicinity may influence the direction of spread of the abscess and the situation of resulting sinuses. When the abscess is allowed to burst, or is opened and becomes infected with pyogenic bacteria, there is not only the risk of aggravation of the disease and persistent suppuration, but there is a greater liability to general tuberculosis.

The sinuses may be so tortuous that a probe cannot be passed to the primary focus of disease, and their course and disposition can only be demonstrated by injecting the sinuses with an emulsion of bismuth and taking X-ray photographs.

Tuberculous infection of the lymph glands of the limb is exceptional, but may follow upon infection of the skin around the orifice of a sinus.

A slight rise of temperature in the evening may be induced in quiescent joint lesions by injury or by movement of the joint under anaesthesia, or by the fatigue of a railway journey. When sinuses have formed and become infected with pyogenic bacteria, there may be a diurnal variation in the temperature of the type known as hectic fever (Fig. 11).

_Relative Frequency of Tuberculous Disease in Different Joints._--Hospital statistics show that joints are affected in the following order of frequency: Spine, knee, hip, ankle and tarsus, elbow, wrist, shoulder. The hip and spine are most often affected in childhood and youth, the shoulder and wrist in adults; the knee, ankle, and elbow show little age preference.

_Clinical Variations of Tuberculous Joint Disease._--The above description applies to tuberculous joint disease in general; it must be modified to include special manifestations or varieties.

When the main incidence of the infection affects the synovial membrane, the clinical picture may assume the form of a _hydrops_, or of an _empyema_ in which the joint is filled with pus. More common than either of these is the well-known _white swelling_ or _tumor albus_ (Wiseman, 1676) which is the clinical manifestation of diffuse thickening of the synovial membrane along with mucoid degeneration of the peri-synovial cellular tissue. It is well seen in joints which are superficial--such as the knee, ankle, elbow, and wrist. The swelling, which is the first and most prominent clinical feature, develops gradually and painlessly, obliterating the bony prominences by filling up the natural hollows. It appears greater to the eye than is borne out by measurement, being thrown into relief by the wasting of the muscles above and below the joint. In the early stage the swelling is elastic, doughy, and non-sensitive, and corresponds to the superficial area of the synovial membrane involved, and there is comparatively little complaint on the part of the patient, because the articular surfaces and ligaments are still intact. There may be a feeling of weight in the limb, and in the case of the knee and ankle the patient tires on walking and drags the leg with more or less of a limp. Movements of the joint are permitted, but are limited in range. The disability is increased by use and exertion, but, for a time at least, it improves under rest.

If the disease is not arrested, there follow the symptoms and signs of involvement of the articular surfaces.

_Influence of Tuberculous Joint Disease on the General Health._--Experience shows that the early stages of tuberculous joint disease are compatible with the appearance of good health. As a rule, however, and especially if there is mixed infection, the health suffers, the appetite is impaired, the patient is easily tired, and there may be some loss of weight.

1. Treatment.#--In addition to the general treatment of tuberculosis,

local measures are employed. These may be described under two heads--the conservative and the operative.

_Conservative treatment_ is almost always to be employed in the first instance, as by it a larger proportion of cures is obtained with a smaller mortality and with better functional results than by operation.

_Treatment by rest_ implies the immobilisation of the diseased limb until pain and tenderness have disappeared. The attitude in which the limb is immobilised should be that in which, in the event of subsequent stiffness, it will be most serviceable to the patient. Immobilisation may be secured by bandages, splints, extension, or other apparatus. _Extension_ with weight and pulley is of value in securing rest, especially in disease of the hip or knee; it eliminates muscular spasm, relieves pain and startings at night, and prevents abnormal attitudes of the limb. If, when the patient first comes under observation, the limb is in a deformed attitude which does not readily yield to extension, the deformity should be corrected under an anaesthetic.

_The induction of hyperaemia_ is often helpful, the rubber bandage or the hot-air chamber being employed for an hour or so morning and evening.

_Injection of Iodoform._--This is carried out on the same lines as have been described for tuberculous abscess. After the fluid contents of the joint are withdrawn, the iodoform is injected; and this may require to be repeated in a month or six weeks.

After the injection of iodoform there is usually considerable reaction, attended with fever (101 F.), headache, and malaise, and considerable pain and swelling of the joint. In some cases there is sickness, and there may be blood pigment in the urine. The severity of these phenomena diminishes with each subsequent injection.

The use of Scott's dressing and of blisters and of the actual cautery has largely gone out of fashion, but the cautery may still be employed with benefit for the relief of pain in cases in which ulceration of cartilage is a prominent feature.

The application of the X-rays has proved beneficial in synovial lesions in superficial joints such as the wrist or elbow; prolonged exposures are made at fortnightly intervals, and on account of the cicatricial contraction which attends upon recovery, the joint must be kept in good position.

Conservative treatment is only abandoned if improvement does not show itself after a thorough trial, or if the disease relapses after apparent cure.

_Operative Treatment._--Other things being equal, operation is more often indicated in adults than in children, because after the age of twenty there is less prospect of recovery under conservative treatment, there is more tendency for the disease to relapse and to invade the internal organs, and there is no fear of interfering with the growth of the bones. The state of the general health may necessitate operation as the most rapid method of removing the disease. The social status of the patient must also be taken into account; the bread-winner, under existing social conditions, may be unable to give up his work for a sufficient time to give conservative measures a fair trial.

The _local conditions_ which decide for or against operation are differently regarded by different surgeons, but it may be said in general terms that operative interference is indicated in cases in which the disease continues to progress in spite of a fair trial of conservative measures; in cases unsuited for conservative treatment--that is to say, where there are severe bone lesions. Operative interference is indicated also when the functional result will be better than that likely to be obtained by conservative measures, as is often the case in the knee and elbow. Cold abscesses should, if possible, be dealt with before operating on the joint.

In many cases the extent of the operation can only be decided after exploration. The aim is to remove all the disease with the least impairment of function and the minimum sacrifice of healthy tissue. The more open the method of operating the better, so that all parts of the joint may be available for inspection. The methods of Kocher, which permit of dislocating the joint, are specially to be recommended, as this procedure affords the freest possible access. Diseased synovial membrane is removed with the scissors or knife. If the cartilages are sound, and if a movable joint is aimed at, they may be left; but if ankylosis is desired, they must be removed. Localised disease of the cartilage should be removed with the spoon or gouge, and the bone beneath investigated. If the articular surface is extensively diseased, a thin slice of bone should be removed, and if foci in the marrow are then revealed, it is better to gouge them out than to remove further slices of bone, as this involves sacrifice of the cortex and periosteum.

Operative treatment of deformities resulting from tuberculous joint disease has almost entirely replaced reduction by force; the contracted soft parts are divided, and the bone is resected.

_Amputation_ for tuberculous joint disease has become one of the rare operations of surgery, and is only justified when less radical measures have failed and the condition of the limb is affecting the general health. Amputation is more frequently called for in persons past middle life who are the subjects of pulmonary tuberculosis.

SYPHILITIC DISEASE

Syphilitic affections of joints are comparatively rare. As in tuberculosis, the disease may be first located in the synovial membrane, or it may spread to the joint from one of the bones.

In #acquired syphilis#, at an early stage and before the skin eruptions appear, one of the large joints, such as the shoulder or knee, may be the seat of pain--_arthralgia_--which is worse at night. In the secondary stage, a _synovitis_ with serous effusion is not uncommon, and may affect several joints. Syphilitic _hydrops_ is met with almost exclusively in the knee; it is frequently bilateral, and is insidious in its onset and progress, the patient usually being able to go about.

In the _tertiary stage_ the joint lesions are persistent and destructive, and result from the formation of gummata, either in the deeper layers of the synovial membrane or in the adjacent bone or periosteum.

_Peri-synovial_ and _peri-bursal gummata_ are met with in relation to the knee-joint of middle-aged adults, especially women. They are usually multiple, develop slowly, and are rarely sensitive or painful. One or more of the gummata may break down and give rise to tertiary ulcers. The co-existence of indolent swellings, ulcers, and depressed scars in the vicinity of the knee is characteristic of tertiary syphilis.

The disease spreads throughout the capsule and synovial membrane, which becomes diffusely thickened and infiltrated with granulation tissue which eats into and replaces the articular cartilage. Clinically, the condition resembles tuberculous disease of the synovial membrane, for which it is probably frequently mistaken, but in the syphilitic affection the swelling is nodular and uneven, and the subjective symptoms are slight, mobility is little impaired, and yet the deformity is considerable.

_Syphilitic osteo-arthritis_ results from a gumma in the periosteum or marrow of one of the adjacent bones. There is gradual enlargement of one of the bones, the patient complains of pains, which are worst at night. The disease may extend to the synovial membrane and be attended with effusion into the joint, or it may erupt on the periosteal surface and invade the skin, forming one or more sinuses. The further progress is complicated by the occurrence of pyogenic infection leading to necrosis of bone, in the knee-joint, for example, the patella or one of the condyles of the femur or tibia, may furnish a sequestrum. In such cases, anti-syphilitic treatment must be supplemented by operation for the removal of the diseased tissues. In the knee, excision is rarely necessary; but in the elbow it may be called for to obtain a movable joint.

In #inherited syphilis# the earliest joint affections are those in which there is an effusion into the joint, especially the knee or elbow; and in exceptional cases pyogenic infection may be superadded, and pus form in the joint.

In older children, a gummatous synovitis is met with of which the most striking features are: its insidious development, its chronic course, symmetrical distribution, freedom from pain, the free mobility of the joint, its tendency to relapse, and its association with other syphilitic stigmata, especially in the eyes. The knees are the joints most frequently affected, and the condition usually yields readily to anti-syphilitic treatment without impairment of function.

JOINT DISEASES ACCOMPANYING CERTAIN CONSTITUTIONAL CONDITIONS

1. Gout.#--_Arthritis Urica._--One of the manifestations of gout is that

certain joints are liable to attacks of inflammation associated with the deposit of a chalk-like material composed of sodium biurate, chiefly in the matrix of the articular cartilage, it may be in streaks or patches towards the central area of the joint, or throughout the entire extent of the cartilage, which appears as if it had been painted over with plaster of Paris. As a result of this uratic infiltration, the cartilage loses its vitality and crumbles away, leading to the formation of what are known as gouty ulcers, and these may extend through the cartilage and invade the bone. The deposit of urates in the synovial membrane is attended with effusion into the joint and the formation of adhesions, while in the ligaments and peri-articular structures it leads to the formation of scar tissue. The metatarso-phalangeal joint of the great toe, on one or on both sides, is that most frequently affected. The disease is met with in men after middle life, and while common enough in England and Ireland, is almost unknown in hospital practice in Scotland.

The _clinical features_ are characteristic. There is a sudden onset of excruciating pain, usually during the early hours of the morning, the joint becomes swollen, red, and glistening, with engorgement of the veins and some fever and disturbance of health and temper. In the course of a week or ten days there is a gradual return to the normal. Such attacks may recur only once a year or they may be more frequent; the successive attacks tend to become less acute but last longer, and the local phenomena persist, the joint remaining permanently swollen and stiff. Masses of chalk form in and around the joint, and those in the subcutaneous tissue may break through the skin, forming indolent ulcers with exposure of the chalky masses (_tophi_). The hands may become seriously crippled, especially when the tendon sheaths and bursae also are affected; the crippling resembles that resulting from arthritis deformans but it differs in not being symmetrical.

The local _treatment_ consists in employing soothing applications and a Bier's bandage for two or three hours twice daily while the symptoms are acute; later, hot-air baths, massage, and exercises are indicated. It is remarkable how completely even the most deformed joints may recover their function. Dietetic and medicinal treatment must also be employed.

1. Chronic Rheumatism.#--This term is applied to a condition which

sometimes follows upon acute articular rheumatism in persons presenting a family tendency to acute rheumatism or to inflammations of serous membranes, and manifesting other evidence of the rheumatic taint, such as chorea or rheumatic nodules.

The changes in the joints involve almost exclusively the synovial membrane and the ligaments; they consist in cellular infiltration and exudation, resulting in the formation of new connective tissue which encroaches on the cavity of the joint and gives rise to adhesions, and by contracting causes stiffness and deformity. The articular cartilages may subsequently be transformed into connective tissue, with consequent fibrous ankylosis and obliteration of the joint. The bones are affected only in so far as they undergo fatty atrophy from disuse of the limb, or alteration in their configuration as a result of partial dislocation. Osseous ankylosis may occur, especially in the small joints of the hand and foot.

The disease is generally poly-articular and may be met with in childhood and youth as well as in adult life. In some cases pain is so severe that the patient resists the least attempt at movement. In others, the joints, although stiff, can be moved but exhibit pronounced crackings. When there is much connective tissue formed in relation to the synovial membrane, the joint is swollen, and as the muscles waste above and below, the swelling is spindle-shaped. Subacute exacerbations occur from time to time, with fever and aggravation of the local symptoms and implication of other joints. After repeated recurrences, there is ankylosis with deformity, the patient becoming a helpless cripple. On account of the tendency to visceral complications, the tenure of life is uncertain.

From the nature of the disease, _treatment_ is for the most part palliative. Salicylates are only of service during the exacerbations attended with pyrexia. The application of soda fomentations, turpentine cloths, or electric or hot-air baths may be useful. Improvement may result from the general and local therapeutics available at such places as Bath, Buxton, Harrogate, Strathpeffer, Wiesbaden, or Aix. In selected cases, a certain measure of success has followed operative interference, which consists in a modified excision. The deformities resulting from chronic rheumatism are but little amenable to surgical treatment, and forcible attempts to remedy stiffness or deformity are to be avoided.

1. Arthritis Deformans# (_Osteo-arthritis, Rheumatoid Arthritis, Rheumatic

Gout, Malum Senile, Traumatic or Mechanical Arthritis_).--Under the term arthritis deformans, which was first employed by Virchow, it is convenient to include a number of joint affections which have many anatomical and clinical features in common.

The disease is widely distributed in the animal kingdom, both in domestic species and in wild animals in the natural state such as the larger carnivora and the gorilla; evidence of it has also been found in the bones of animals buried with prehistoric man.

The morbid changes in the joints present a remarkable combination of atrophy and degeneration on the one hand and overgrowth on the other, indicating a profound disturbance of nutrition in the joint structures. The nature of this disturbance and its etiology are imperfectly known. By many writers it is believed to depend upon some form of auto-intoxication, the toxins being absorbed from the gastro-intestinal tract, and those who suffer are supposed to possess what has been called an "arthritic diathesis."

The localisation of the disease in a particular joint may be determined by several factors, of which trauma appears to be the most important. The condition is frequently observed to follow, either directly or after an interval, upon a lesion which involves gross injury of the joint or of one of the neighbouring bones. It occurs with greater frequency after repeated minor injuries affecting the joint and its vicinity, such as sprains and contusions, and particularly those sustained in laborious occupations. This connection between trauma and arthritis deformans led Arbuthnot Lane to apply to it the term _traumatic_ or _trade arthritis_.

The traumatic or strain factor in the production of the disease may be manifested in a less obvious fashion. In the lower extremity, for example, _any condition which disturbs the static equilibrium of the limb as a whole_ would appear to predispose to the disease in one or other of the joints. The static equilibrium may be disturbed by such deformities as flat-foot or knock-knee, and badly united fractures of the lower extremity. In hallux valgus, the metatarso-phalangeal joint of the great toe undergoes changes characteristic of arthritis deformans.

A number of cases have been recorded in which arthritis deformans has followed upon antecedent disease of the joint, such as pyogenic or gonorrhoeal synovitis, upon repeated haemorrhages into the knee-joint in bleeders, and in unreduced dislocations in which a new joint has been established.

[Illustration: FIG. 157.--Arthritis Deformans of Elbow, showing destruction of articular surfaces and masses of new bone around the articular margins.

(Anatomical Museum, University of Edinburgh.)]

Lastly, Poncet and other members of the Lyons school regard arthritis deformans as due to an attenuated form of tuberculous infection, and draw attention to the fact that a tuberculous family history is often met with in the subjects of the disease.

[Illustration: FIG. 158.--Arthritis Deformans of Knee, showing eburnation and grooving of articular surfaces.

(Anatomical Museum, University of Edinburgh.)]

_Morbid Anatomy._--The commonest type is that in which the articular surfaces undergo degenerative changes. The primary change involves the articular cartilage, which becomes softened and fibrillated and is worn away until the subjacent bone is exposed. If the bone is rarefied, the enlarged cancellous spaces are opened into and an eroded and worm-eaten appearance is brought about; with further use of the joint, the bone is worn away, so that in a ball-and-socket joint like the hip, the head of the femur and the acetabulum are markedly altered in size and shape. More commonly, the bone exposed as a result of disappearance of the cartilage is denser than normal, and under the influence of the movements of the joint, becomes smooth and polished--a change described as _eburnation_ of the articular surfaces (Fig. 158). In hinge-joints such as the knee and elbow, the influence of movement is shown by a series of parallel grooves corresponding to the lines of friction (Fig. 158).

[Illustration: FIG. 159.--Hypertrophied Fringes of Synovial Membrane in Arthritis Deformans of Knee.

(Museum of Royal College of Surgeons, Edinburgh.)]

While these degenerative changes are gradually causing destruction of the articular surfaces, reparative and hypertrophic changes are taking place at the periphery. Along the line of the junction between the cartilage and synovial membrane, the proliferation of tissue leads to the formation of nodules or masses of cartilage--_ecchondroses_--which are subsequently converted into bone (Fig. 157). Gross alterations in the ends of the bone are thus brought about which can be recognised clinically and in skiagrams, and which tend to restrict the normal range of movement. The extension of the ossification into the synovial reflection and capsular ligament adds a collar or "lip" of new bone, known as "lipping" of the articular margins, and also into other ligaments, insertions of tendons and intermuscular septa giving rise to bony outgrowths or osteophytes not unlike those met with in the neuro-arthropathies.

Proliferative changes in the synovial membrane are attended with increased vascularity and thickening of the membrane and an enlargement of its villi and fringes. When the fatty fringes are developed to an exaggerated degree, the condition is described as an _arborescent lipoma_ (Fig. 159). Individual fringes may attain the size of a hazel nut, and the fibro-fatty tissue of which they are composed may be converted into cartilage and bone; such a body may remain attached by a narrow pedicle or stalk, or this may be torn across and the body becomes loose and, unless confined in a recess of the joint, it wanders about and may become impacted between the articular surfaces. These changes in the synovial membrane are often associated with an abundant exudate or hydrops. These degenerative and hypertrophic changes, while usually attended with marked restriction of movement and sometimes by "locking" of the joint, practically never result in ankylosis.

The _ankylosing type_ of chronic arthritis is fortunately much rarer than those described above, and is chiefly met with in the joints of the fingers and toes and in those of the vertebral column. The synovial membrane proliferates, grows over the cartilage, and replaces it, and when two such articular surfaces are in contact they tend to adhere, thus obliterating the joint, cavity, and resulting in fibrous or bony ankylosis. The changes progress slowly and, before they result in ankylosis, various sub-luxations and dislocations may occur with distortion and deformity which, in the case of the fingers, is extremely disabling and unsightly (Fig. 160).

_Clinical Features._--It is usually observed that in patients who are still young the tendency is for the disease to advance with considerable rapidity, so that in the course of months it may cause crippling of several joints. The course of the disease as met with in persons past middle life is more chronic; it begins insidiously, and many years may pass before there is pronounced disability. The earliest symptom is stiffness, especially in the morning after rest, which passes off temporarily with use of the limb. As time goes on, the range of movement becomes restricted, and crackings occur. This stage of the disease may be prolonged indefinitely; if it progresses, stiffness becomes more pronounced, certain movements are lost, others develop in abnormal directions, and deformed attitudes add to the disablement. The disease is compatible with long life, but not with any active occupation, hence those of the hospital class who suffer from it tend to accumulate in workhouse infirmaries.

_Hydrops_ is most marked in the knee, and may affect also the adjacent bursae. As the joint becomes distended with fluid, the ligaments are stretched, the limb becomes weak and unstable, and the patient complains of a feeling of weight, of insecurity, and of tiredness. Pain is occasional and evanescent, and is usually the result of some extra exertion, or exposure to cold and wet. This form of the disease is extremely chronic, and may last for an indefinite number of years. It is to be diagnosed from the other forms of hydrops already considered--the purely traumatic, the pyogenic, gonorrhoeal, tuberculous, and syphilitic--and from that associated with Charcot's disease.

_Hypertrophied fringes and pedunculated or loose bodies_ often co-exist with hydrops, and give rise to characteristic clinical features, particularly in the knee. The fringes, especially when they assume the type of the arborescent lipoma, project into the cavity of the joint, filling up its recesses and distending its capsule so that the joint is swollen and slightly flexed. Pain is not a prominent feature, and the patient may walk fairly well. On grasping the joint while it is being actively flexed and extended, the fringes may be felt moving under the fingers. Symptoms from impaction of a loose body are exceptional.

[Illustration: FIG. 160.--Arthritis Deformans of Hands, showing symmetry of lesions, ulnar deviation of fingers, and nodular thickening at inter-phalangeal joints.]

_The dry form of arthritis deformans_, although specially common in the knee, is met with in other joints, either as a mon-articular or poly-articular disease; and it is also met with in the joints of the spine and of the fingers as well as in the temporo-mandibular joint. In the joints of the fingers the disease is remarkably symmetrical, and tends to assume a nodular type (Heberden's nodes) (Fig. 160); in younger subjects it assumes a more painful and progressive fusiform type (Fig. 161). In the larger joints the subjective symptoms usually precede any palpable evidence of disease, the patient complaining of stiffness, crackings, and aching, aggravated by changes in the weather. The roughness due to fibrillation of the articular cartilages causes coarse friction on moving the joint, or, in the knee, on moving the patella on the condyles of the femur. It may be months or even years before the lipping and other hypertrophic changes in the ends of the bones are recognisable, and before the joint assumes the deformed features which the name of the disease suggests.

The capsular ligament, except in hydrops, is the seat of connective-tissue overgrowth, and tends to become contracted and rigid. Intra-articular ligaments, such as the ligamentum teres in the hip, are usually worn away and disappear. The surrounding muscles undergo atrophy, tendons become adherent to their sheaths and may be ossified, and the sheaths of nerves may be involved by the cicatricial changes in the surrounding tissues.

_The X-ray appearances of arthritis deformans_ necessarily vary with the type of the disease and the joint affected; in the joints of the fingers there is a narrowing of the spaces between the articular ends of the bones as a result of absorption of the articular cartilage, and rarefaction of the cancellous tissue in the vicinity of the joints; in the larger joints there is "lipping" of the articular margins, osteophytes, and other evidence of abnormal ossification in and around the joint. Eburnation of the articular surfaces is shown by increase in the density of the shadow of the bone in the areas affected.

[Illustration: FIG. 161.--Arthritis Deformans affecting several Joints, in a boy aet. 10.

(Dr. Dickson's case.)]

_Treatment._--Treatment is for the most part limited to the relief of symptoms. On no account should the affected joints be kept at rest by means of splints or other apparatus. Active movements and exercises of all kinds are to be persevered with. When pain is a prominent feature, it may be relieved either by douches of iodine and hot water (tincture of iodine 1 oz. to the quart), or by the application of lint saturated with a lotion made up of chloral hydrate, gr. v, glycerin [dram]j, water [ounce]j, and covered with oil-silk. Strain and over-use of the joint and sudden changes of temperature are to be avoided. The induction of hyperaemia by means of massage, the elastic bandage, and hot-air baths is often of service. Operative interference is indicated when the disease is of a severe type, when it is mon-articular, and when the general condition of the patient is otherwise favourable. Excision has been practised with success in the hip, knee, elbow, and temporo-mandibular joints. Limitation of movement and locking at the hip-joint when due to new bone round the edge of the acetabulum may be greatly relieved by removal of the bone--a procedure known as _cheilotomy_. Loose bodies and hypertrophied fringes if causing symptoms may also be removed by operation.

When stiffness and grating on movement are prominent features we have found the injection of from half to one ounce of sterilised white vaseline afford decided relief.

The patient should be nourished well, and there need be no restriction in the diet such as is required in gouty patients, so long as the digestion is not impaired. Benefit is also derived from the administration of cod-liver oil, and of tonics, such as strychnin, arsenic, and iron, and in some cases of iodide of potassium. Luff recommends the administration over long periods of guaiacol carbonate, in cachets beginning with doses of 5-10 grs. and increased to 15-20 grs. thrice daily. A course of treatment at one of the reputed spas--Aix, Bath, Buxton, Gastein, Harrogate, Strathpeffer, Wiesbaden, Wildbad--is often beneficial.

In some cases benefit has followed the prolonged internal administration of liquid paraffin.

On the assumption that the condition is the result of an auto-intoxication from the intestinal tract, saline purges and irrigation of the colon are indicated, and Arbuthnot Lane claims to have brought about improvement by short-circuiting or by resecting the colon.

Residence in a warm and dry climate, with an open-air life, has been known to arrest the disease when other measures have failed to give relief.

The application of radium and the ingestion of radio-active waters have also been recommended.

1. Haemophilic# or #Bleeder's Joint#.--This is a rare but characteristic

affection met with chiefly in the knee-joint of boys who are the subjects of haemophilia. After some trivial injury, or even without apparent cause, a haemorrhage takes place into the joint. The joint is tensely swollen, cannot be completely extended, and is so painful that the patient is obliged to lie up. The temperature is often raised (101 to 102 F.), especially if there are also haemorrhages elsewhere. The blood in the joint is slowly re-absorbed, and by the end of a fortnight or so, the symptoms completely disappear. As a rule these attacks are repeated; the pain attending them diminishes, but the joint becomes the seat of permanent changes: the synovial membrane is thickened, abnormally vascular, and coloured brown from the deposit of blood pigment; on its surface, and in parts of the articular cartilage, there is a deposit of rust-coloured fibrin; there may be extensive adhesions, and in some cases changes occur like those observed in arthritis deformans with erosion and ulceration of the cartilage and a form of dry caries of the articular surfaces, which may terminate in ankylosis.

As the swelling of the joint is associated with wasting of the muscles, with stiffness, and with flexion, the condition closely resembles tuberculous disease of the synovial membrane. From errors in diagnosis such joints have been operated upon, with disastrous results due to haemorrhage.

The treatment of a recent haemorrhage consists in securing absolute rest and applying elastic compression. The introduction of blood-serum (10-15 c.c.) into a vein may assist in arresting the haemorrhage; anti-diphtheritic serum is that most readily obtainable.

After an interval, measures should be adopted to promote the absorption of blood and to prevent stiffness and flexion; these include massage, movements, and extension with weight and pulley.

JOINT DISEASES ASSOCIATED WITH LESIONS OF THE NERVOUS SYSTEM: NEURO-ARTHROPATHIES

_In Lesions of Peripheral Nerves._--In the hand, and more rarely in the foot, when one or other of the main nerve-trunks has been divided or compressed, the joints may become swollen and painful and afterwards become stiff and deformed. Bony ankylosis has been observed.

_In Affections of the Spinal Medulla._--In myelitis, progressive muscular atrophy, poliomyelitis, insular sclerosis, and in traumatic lesions, joint affections are occasionally met with.

The occurrence of joint lesions in _locomotor ataxia_ (tabes dorsalis) was first described by Charcot in 1868--hence the term "Charcot's disease" applied to them. Although they usually develop in the ataxic stage, one or more years after the initial spinal symptoms, they may appear before there is any evidence of tabes. The onset is frequently determined by some injury. The joints of the lower extremity are most commonly affected, and the disease is bilateral in a considerable proportion of cases--both knees or both hips, for instance, being implicated.

Among the theories suggested in explanation of these arthropathies the most recent is that by Babinski and Barre, which traces the condition to vascular lesions of a syphilitic type in the articular arteries.

The first symptom is usually a swelling of the joint and its vicinity. There is no redness or heat and no pain on movement. The peri-articular swelling, unlike ordinary oedema, scarcely pits even on firm pressure.

[Illustration: FIG. 162.--Bones of Knee-joint in advanced stage of Charcot's Disease. The medial part of the head of the tibia has disappeared.

(Anatomical Museum, University of Edinburgh).]

In mild cases this condition of affairs may persist for months; in severe cases destructive changes ensue with remarkable rapidity. The joint becomes enormously swollen, loses its normal contour, and the ends of the bones become irregularly deformed (Fig. 162). Sometimes, and especially in the knee, the clinical features are those of an enormous hydrops with fibrinous and other loose bodies and hypertrophied fringes--and great oedema of the peri-articular tissues (Fig. 163). The joint is wobbly or flail-like from stretching and destruction of the controlling ligaments, and is devoid of sensation. In other cases, wearing down and total disappearance of the ends of the bones is the prominent feature, attended with flail-like movements and with coarse grating. Dislocation is observed chiefly at the hip, and is rather a gross displacement with unnatural mobility than a typical dislocation, and it is usually possible to move the bones freely upon one another and to reduce the displacement. A striking feature is the extensive formation of new bone in the capsular ligament and surrounding muscles. The enormous swelling and its rapid development may suggest the growth of a malignant tumour. The most useful factor in diagnosis is the entire absence of pain, of tenderness, and of common sensibility. The freedom with which a tabetic patient will allow his disorganised joint to be handled requires to be seen to be appreciated.

[Illustration: FIG. 163.--Charcot's Disease of Left Knee. The joint is distended with fluid and the whole limb is oedematous.]

The rapidity of the destructive changes in certain cases of tabes, and the entire absence of joint lesions in others, would favour the view that special parts of the spinal medulla must be implicated in the former group.

In _syringomyelia_, joint affections (gliomatous arthropathies) are more frequent than in tabes, and they usually involve the upper extremity in correspondence with the seat of the spinal lesion, which usually affects the lower cervical and upper thoracic segments. Except that the joint disease is seldom symmetrical, it closely resembles the arthropathy of tabes. The completeness of the analgesia of the articular structures and of the overlying soft parts is illustrated by the fact that in one case the patient himself was in the habit of letting out the fluid from his elbow with the aid of a pair of scissors, and that in another the joint was painlessly excised without an anaesthetic.

[Illustration: FIG. 164.--Charcot's Disease of both Ankles: front view. Man, aet. 32.]

The disease may become arrested or may go on to complete disorganisation; suppuration may ensue from infection through a breach of the surface, and in rare cases the joint has become the seat of tuberculosis.

[Illustration: FIG. 165.--Charcot's Disease of both Ankles: back view. Man, aet. 32.]

_Treatment_, in addition to that of the nerve lesion underlying the arthropathy, consists in supporting and protecting the joint by means of bandages, splints, and other apparatus. In the lower extremity, the use of crutches is helpful in taking the strain off the affected limb. When there is much distension of the joint, considerable relief follows upon withdrawal of fluid. The best possible result being rigid ankylosis in a good position, it may be advisable to bring this about artificially by arthrodesis or resection. Operation is indicated when only one joint is affected and when the cord lesion is such as will permit of the patient using the limb. The wounds heal well, but the victims of tabes are unfavourable subjects for operative interference, on account of their liability to intercurrent complications. When the limb is quite useless, amputation may be the best course.

_In cerebral lesions_ attended with hemiplegia, joint affections, characterised by evanescent pain, redness, and swelling, are occasionally met with. The secondary changes in joints which are the seat of paralytic contracture are considered with the surgery of the Extremities.

In cases of _hysteria_ and other _functional affections of the nervous system_, an intermittent neuropathic hydrops has been observed--especially in the knee. Without apparent cause, the joint fills with fluid and its movements become restricted, and after from two to eight days the swelling subsides and the joint returns to normal. A remarkable feature of the condition is that the effusion into the joint recurs at regular intervals, it may be over a period of years. Psychic conditions have been known to induce attacks, and sometimes to abort them or even to cause their disappearance. Hence it has been recommended that treatment by suggestion should be employed along with tonic doses of quinine and arsenic.

HYSTERICAL OR MIMETIC JOINT AFFECTIONS

Under this heading, Sir Benjamin Brodie, in 1822, described an affection of joints, characterised by the prominence of subjective symptoms and the absence of pathological changes. Although most frequently met with in young women with an impressionable nervous system, and especially among those in good social circumstances, it occurs occasionally in men. The onset may be referred to injury or exposure to cold, or may be associated with some disturbance of the emotions or of the generative organs; or the condition may be an involuntary imitation of the symptoms of organic joint disease presented by a relative or friend.

It is characteristic that the symptoms develop abruptly without satisfactory cause, that they are exaggerated and wanting in harmony with one another, and that they do not correspond with the features of any of the known forms of organic disease. In some cases the only complaint is of severe pain; more often this is associated with excessive tenderness and with impairment of the functions of the joint. On examination the joint presents a normal appearance, but the skin over it is remarkably sensitive. A light touch is more likely to excite pain than deep and firm pressure. Stiffness is a variable feature--in some cases amounting to absolute rigidity, so that no ordinary force will elicit movement. It is characteristic of this, as of other neuroses, that the symptoms come and go without sufficient cause. When the patient's attention is diverted, the pain and stiffness may disappear. There is no actual swelling of the joint, although there may be an appearance of this from wasting of the muscles above and below. If the joint is kept rigid for long periods, secondary contracture may occur--in the knee with flexion, in the hip with flexion and adduction.

The _diagnosis_ is often a matter of considerable difficulty, and the condition is liable to be mistaken for such organic lesions as a tuberculous or pyogenic focus in the bone close to the joint.

The greatest difficulty is met with in the knee and hip, where the condition may closely simulate tuberculous disease. The use of the Rontgen rays, or examination of the joint under anaesthesia, is helpful.

The _local treatment_ consists chiefly in improving the nutrition of the affected limb by means of massage, exercises, baths, and electricity. Splints are to be avoided. In refractory cases, benefit may follow the application of blisters or of Corrigan's button. The general condition of the patient must be treated on the same lines as in other neuroses. The Weir-Mitchell treatment may have to be employed in obstinate cases, the patient being secluded from her friends and placed in charge of a nurse. Complete recovery is the rule, but when the muscles are weak and wasted from prolonged disuse, a considerable time may elapse before the limb returns to normal.

TUMOURS AND CYSTS

New growths taking origin in the synovial membrane are rare, and are not usually diagnosed before operation. They are attended with exudation into the joint, and in the case of _sarcoma_ the fluid is usually blood-stained. If the tumour projects in a polypoidal manner into the joint, it may cause symptoms of loose body. One or two cases have been recorded in which a _cartilaginous tumour_ growing from the synovial membrane has erupted through the joint capsule and infiltrated the adjoining muscles. _Multiple cartilaginous tumours_ forming loose bodies are described on p. 544.

_Cysts of joints_ constitute an ill-defined group which includes ganglia formed in relation to the capsular ligament. Cystic distension of bursae which communicate with the joint is most often met with in the region of the knee in cases of long-standing hydrops. It was suggested by Morrant Baker that cystic swellings may result from the hernial protrusion of the synovial membrane between the stretched fibres of the capsular ligament, and the name "Baker's cysts" has been applied to these.

In the majority of cases, cysts in relation to joints give rise to little inconvenience and may be left alone. If interfered with at all, they should be excised.

LOOSE BODIES

It is convenient to describe the varieties of loose bodies under two heads: those composed of fibrin, and those composed of organised connective tissue.

1. Fibrinous Loose Bodies# (Corpora oryzoidea).--These are homogeneous or

concentrically laminated masses of fibrin, sometimes resembling rice grains, melon seeds, or adhesive wafers, sometimes quite irregular in shape. Usually they are present in large numbers, but sometimes there is only one, and it may attain considerable dimensions. They are not peculiar to joints, for they are met with in tendon sheaths and bursae, and their origin from synovial membrane may be accepted as proved. They occur in tuberculosis, arthritis deformans, and in Charcot's disease, and their presence is almost invariably associated with an effusion of fluid into the joint. While they may result from the coagulation of fibrin-forming elements in the exudate, their occurrence in tuberculous hydrops would appear to be the result of coagulation necrosis, or of fibrinous degeneration of the surface layer of the diseased synovial membrane. However formed, their shape is the result of mechanical influences, and especially of the movement of the joint.

_Clinically_, loose bodies composed of fibrin constitute an unimportant addition to the features of the disease with which they are associated. They never give rise to the classical symptoms associated with impaction of a loose body between the articular surfaces. Their presence may be recognised, especially in the knee, by the crepitating sensation imparted to the fingers of the hand grasping the joint while it is flexed and extended by the patient.

The _treatment_ is directed towards the disease underlying the hydrops. If it is desired to empty the joint, this is best done by open incision.

[Illustration: FIG. 166.--Radiogram of Multiple Loose Bodies in Knee-joint and Semi-membranosus Bursa in a man aet. 38.

(Mr. J. W. Dowden's case.)]

1. Bodies composed of Organised Connective Tissue.#--These are

comparatively common in joints that are already the seat of some chronic disease, such as arthritis deformans, Charcot's arthropathy, or synovial tuberculosis. They take origin almost exclusively from an erratic overgrowth of the fringes of the synovial membrane, and may consist entirely of fat, the arborescent lipoma (Fig. 159) being the most pronounced example of this variety. Fibrous tissue or cartilage may form in one or more of the fatty fringes and give rise to hard nodular masses, which may attain a considerable size, and in course of time may undergo ossification.

Like other hypertrophies on a free surface, they tend to become pedunculated, and so acquire a limited range of movement. The pedicle may give way and the body become free. In this condition it may wander about the joint, or lie snugly in one of its recesses until disturbed by some sudden movement. A loose body free in a joint is capable of growth, deriving the necessary nutriment from the surrounding fluid. The size and number of the bodies vary widely. Single specimens have been known to attain the size of the patella. The smaller varieties may number considerably over a hundred.

[Illustration: FIG. 167.--Loose Body from Knee-joint of man aet. 25. Natural size.

a = Convex surface. b = Concave surface.]

In arthritis deformans a rarer type of loose body is met with, a portion of the lipping of one of the articular margins being detached by injury. In Charcot's disease, bodies composed of bone are formed in relation to the capsular and other ligaments, and may be made to grate upon one another.

The _clinical features_ in this group are mainly those of the disease which has given rise to the loose bodies, and it is exceptional to meet with symptoms from impaction of the body between the articular surfaces. Treatment is to be directed towards the primary disease in the joint, as well as to the removal of the loose bodies.

[Illustration: FIG. 168.--Multiple partially ossified Chondromas of Synovial Membrane, from Shoulder-joint, the seat of arthritis deformans, from a man aet. 35.]

_Loose Bodies in Joints which are otherwise healthy._--It is in joints otherwise healthy that loose bodies causing the classical symptoms and calling for operative treatment are most frequently met with. They occur chiefly in the knee and elbow of healthy males under the age of thirty. The complaint may be of vague pains, of occasional cracking on moving the joint, or of impairment of function--usually an inability to extend or flex the joint completely. In many cases a clear account is given of the symptoms which arise when the body is impacted between the articular surfaces, namely, sudden onset of intense sickening pain, loss of power in the limb and locking of the joint, followed by effusion and other accompaniments of a severe sprain. On some particular movement, the body is disengaged, the locking disappears, and recovery takes place. Attacks of this kind may recur at irregular intervals, during a period of many years. On examining the joint, it is usually found to contain fluid, and there may be points of special tenderness corresponding to the ligaments that have been overstretched. In cases in which there has been recurrent attacks of locking, the ligaments become slack, the joint is wobbly, and the quadriceps is wasted. The patient himself, or the surgeon, may discover the loose body and feel it roll beneath his fingers, especially if it is lodged in the supra-patellar pouch in the knee, or on one or other side of the olecranon in the elbow. In most instances the patient has carefully observed his own symptoms, and is aware not only of the existence of the loose body, but of its erratic appearance at different parts of the joint. This feature serves to differentiate the lesions from a torn medial meniscus in which the pain and tenderness are always in the same spot. As the body usually contains bone, it is recognisable in a skiagram.

[Illustration: FIG. 169.--Multiple Cartilaginous Loose Bodies from Knee-joint.]

There are two methods of _removing the body_; the first and simpler method is applicable when the body can be palpated, usually in the supra-patellar pouch; it is preferably transfixed by a needle and can then be removed through a small incision; otherwise, the joint must be freely opened and explored, firstly to find the body and further to remove it.

The characters of this type of loose body are remarkably constant. It is usually solitary, about the size of a bean or almond, concavo-convex in shape, the convex aspect being smooth like an articular surface, the concave aspect uneven and nodulated and showing reparative changes, healing over of the raw surface, and the new formation of fibrous tissue, hyaline cartilage and bone, the necessary nutriment being derived from the synovial fluid (Fig. 167). The body is sometimes found to be lodged in a defect or excavation in one of the articular surfaces, usually the medial condyle of the femur, from which it is readily shelled out by means of an elevator. It presents on section a layer of articular cartilage on the convex aspect and a variable thickness of spongy bone beneath this.

The origin of these bodies is one of the most debated questions in surgical pathology; they obviously consist of a portion of the articular surface of one of the bones, but how this is detached still remains a mystery; some maintain that it is purely traumatic; Konig regards them as portions of the articular surface which have been detached by a morbid process which he calls "osteochondritis dessicans."

_Multiple Chondromas and Osteomas of the Synovial Membrane._--In this rare type of loose body, the surface of the synovial membrane is studded with small sessile or pedunculated tumours composed of pure hyaline cartilage, or of bone, or of transition stages between cartilage and bone. They are pearly white in colour, pitted and nodular on the surface, rarely larger than a pea, although when compressed they may cake into masses of considerable size. With the movements of the joint many of the tumours become detached and lie in the serous exudate excited by their presence. They are found also in the diverticula of the synovial membrane, in the shoulder in the downward prolongation along the tendon of the biceps, in the hip in the bursal extension beneath the psoas.

The patient complains of increasing disability of the limb, movements of the joint becoming more and more restricted and painful. There is swelling corresponding to the distended capsule of the joint, and on palpation the bodies moving under the fingers yield a sensation as of grains of rice shifting in a bag. If the bodies are so numerous as to be tightly packed together, the impression is that of a plastic mass having the shape of the synovial sac. The stiffness and the cracking on movement may suggest arthritis deformans, but the X-ray appearances make the diagnosis an easy one. We have observed two cases of this affection in the knee-joint of adult women, one in the shoulder-joint of an adult male (Fig. 168), and Caird has observed one in the hip. The treatment consists in opening the joint by free incision and removing the bodies.

_Displacement of the menisci_ of the knee is referred to with injuries of that joint.