RHEUMATOID ARTHRITIS (Rheumatoid polyarthritis)

Rheumatoid arthritis is a chronic inflammation of joints, often associated with mild constitutional symptoms. It nearly always affects several joints at the same time (polyarthritis). Joint changes of a similar nature also occur in a number of other conditions such as juvenile chronic arthritis (Still’s disease), Reiter’s syndrome, psoriasis, lupus erythematosus, and other connective tissue or collagen diseases.

Cause. The cause is unknown. At present only two possibilities attract serious consideration:

The hypothesis of auto-immunity, possibly to type II collagen, is based mainly on the observation that the serum of many patients with rheumatoid arthritis contains an antibody known as rheumatoid factor, which reacts with the body protein gamma globulin. When the antibody is present the disease is termed ‘sero-positive’, as contrasted with sero-negative arthritis when the antibody is absent. The source of the antigen, and many other details of the mechanism by which rheumatoid factor is formed, are unknown.

The hypothesis of infection is likewise without sure foundation. Infection – possibly by a virus or by organisms of the mycoplasma or diphtheroid group – may result in liberation of antigenic type II collagen from the patient’s own articular cartilage.

Pathology. The synovial membrane is thickened by chronic inflammatory changes: characteristically it is infiltrated with macrophage-like cells and T-cell lymphocytes (Fig. 9.1). Later the articular cartilage is gradually softened and eroded, and the subchondral bone may also be eroded, characteristically at the joint margins – probably from the action of lytic enzymes and inflammatory mediators produced in the thickened synovial membrane. The eroded surfaces become covered by a soft membrane of inflammatory tissue known as ‘pannus’.

Fig. 9.1 Rheumatoid arthritis, with possible results. In the active phase there is marked thickening of the synovial membrane. Later, the articular cartilage is often eroded and in severe cases there may be some destruction of bone. The possible results are: 1. restoration to normal (only after mild disease of short duration); 2. continuing mildly active disease with permanently damaged joint surfaces and restricted movement; and 3. secondary osteoarthritis from wear-and-tear degeneration of the damaged joint surfaces.

The pathological changes are not confined to joints. The synovial lining of tendon sheaths may be similarly inflamed and thickened, both in the hands and in the feet. The contained tendons may become softened and may rupture, aggravating any existing deformity. Inflammatory nodules may form in the soft tissues.

After months or years of activity the disease process tends to become less active, usually leaving a number of joints that are permanently damaged, with consequent deformity, instability, or ankylosis.

Clinical features. The patient is usually a young or middle-aged adult, and is more likely to be a woman than a man. Any joint may be affected, but the incidence is higher in the more peripheral joints such as the hand joints, wrists, feet, knees, and elbows than in the lumbar or thoracic spine, shoulders, or hips. The onset is gradual, with increasing pain and swelling of a joint. Soon a number of other joints are similarly affected. Pain and stiffness are often worst when activity is resumed after resting. Often there is constitutional disturbance, with tiredness and anaemia, and occasionally fever.

On examination the affected joints are swollen from synovial thickening. The overlying skin is warmer than normal. The range of joint movements is restricted, and movement causes pain, especially at the extremes. These clinical features are often more severe in sero-positive disease than when rheumatoid factor is absent from the serum.

It is important always to study the condition of the cervical spine, which is commonly affected. Despite relatively minor symptoms, destruction of ligaments and bone may sometimes lead to subluxation of an intervertebral joint of such degree that the spinal cord is endangered, and it is important always to be wary of this possibility.

Extra-articular features may include enlargement of lymph nodes, muscle wasting, subcutaneous rheumatoid nodules, and anaemia.

Imaging. Radiographic features: At first there is no alteration from the normal. Later, there is diffuse rarefaction in the area of the joint. Eventually destruction of joint cartilage may lead to narrowing of the cartilage space and, in severe cases, to localised erosion of the bone ends (Fig. 9.2) especially in periarticular sites. Radioisotope bone scanning shows increased uptake of the isotope in the region of affected joints.

Fig. 9.2 Joint damage in rheumatoid arthritis. Left. Long-established rheumatoid arthritis of the knee. Note the rarefaction and loss of cartilage space. Right. Destruction of the elbow joint in a case of severe rheumatoid arthritis of long duration.

Investigations. Both the erythrocyte sedimentation rate and C-reactive proteins are raised during the active phase. The rheumatoid factor is present in the serum of 80% of patients with rheumatoid arthritis and is detected by the latex fixation or Rose-Waaler sheep cell agglutination tests.

Diagnosis. For a diagnosis of rheumatoid arthritis four of the following seven criteria must be present.

The clue to the diagnosis is the simultaneous involvement of several joints, with raised sedimentation rate. The presence of rheumatoid factor in the blood is highly suggestive, though the tests are not specific for rheumatoid arthritis; and rheumatoid factor may be absent in about 20% of patients even in well-established rheumatoid arthritis.

A search should always be made for evidence of one of the distinct clinical entities that may be associated with joint changes of a rheumatoid type. The most important of such conditions are:

These conditions are all sero-negative, and they may be associated with ankylosing spondylitis.

Course. There is a tendency for rheumatoid arthritis to become quiescent after remaining active for months or years. In most cases there is permanent impairment of joint function. In certain joints – especially in the knees – degenerative changes are often superimposed upon the previous rheumatoid condition, and lead to increasingly severe disability even though the original rheumatoid affection is no longer active.

Treatment. The treatment of rheumatoid arthritis is still evolving, but no specific cure has been found. Innumerable drugs have been tried, but it is by no means certain that any of them has an influence on the duration of the disease or on its eventual outcome in a particular case. Undoubtedly some drugs can mitigate the symptoms, particularly the group of non-steroidal anti-inflammatory drugs (NSAIDs) which also have an analgesic effect in addition to their action in reducing synovial inflammatory changes.

Methods of treatment may be classified into the following categories:

Rest and constitutional treatment. Rest is thought to be beneficial, especially in the early stages of the disease and during an exacerbation. At many centres patients are admitted to hospital at the outset for a period of rest, and sometimes this temporary removal from the home environment, with skilled nursing, regular food, and proper sleep, has a remarkably good effect on the general health, which is often impaired in these cases. Rest for individual joints is also helpful during the initial active stage of inflammation, provided it is not enforced for too long. Convenient light splints for this purpose may be made from expanded polystyrene, or plaster of Paris may be used. Splintage is seldom required for more than a few weeks and should be followed by graduated exercises under the supervision of a physiotherapist.

Drugs. Drugs used in rheumatoid arthritis fall mainly into the categories of the NSAIDs, and the potent anti-inflammatory agents grouped under the heading of corticosteroids. A logical plan is to use aspirin since it has both analgesic and mild anti-inflammatory properties, but to be effective it may have to be given in fairly large doses. Alternative first-line drugs should probably be chosen from the group of NSAIDs, which includes indometacin, ibuprofen, naproxen, phenoprofen and piroxicam. Due regard must be paid to the risk of side effects: gastric pain is a common complaint with most of these drugs, and more serious complications, such as gastric bleeding, are seen occasionally.

A different class of anti-rheumatic agents, to be regarded as second-line drugs, includes the potentially toxic group of compounds containing gold salts, usually given by intra-muscular injection. These must be used with care, but they are thought to be sometimes beneficial and therefore justified in severely afflicted patients who have failed to respond to the first-line drugs. Sulfasalazine, a derivative of sulphapyridine, is now also used increasingly as a second-line drug. Its mode of action is uncertain, but it has the advantage over gold salts of oral administration and fewer side effects. Another drug in this second-line category is penicillamine, the effect of which is comparable to that of gold. This also is potentially toxic for the kidneys and must be used with caution. Also included in this category are certain immuno-suppressive agents, such as azathioprine and methotrexate.

Newer developments in drug therapy have centred on biological molecules manufactured by genetic engineering that can block or reduce the production of destructive cytokines and enzymes from the cells of the rheumatoid synovium. The first of these, anti-tumour necrosis factor (TNF) has given very encouraging results in modifying the disease, but no long-term results are yet available.

The place of corticosteroids in rheumatoid arthritis is still controversial. There is wide agreement that because of their serious side effects they should be avoided altogether in the great majority of patients. There may be a small proportion of severely afflicted patients in whom the advantages outweigh the hazards.

Intra-articular injections. Injections of corticosteroids (usually hydrocortisone) into an affected joint can produce worth-while relief, but the disadvantages have precluded their widespread use. The main disadvantages are:

In general, it is wise to avoid repeated injections.

Physiotherapy. Physiotherapy is widely used and generally beneficial, even though some of the benefit may result from suggestion or ‘placebo effect’ rather than from a direct effect on the disease process. Heat in the form of infra-red radiation or short-wave diathermy is commonly used, but probably the most useful contribution of physiotherapy is active exercises including hydrotherapy, designed both to keep joints as mobile as possible and to maintain useful function in the muscles that control them.

Occupational therapy. Occupational therapy is useful mainly in helping seriously disabled patients to find ways in which they can more easily carry out the various activities of everyday life – bathing, toilet, cooking, feeding, boarding public transport, and many others. Many useful aids for the disabled are available, and those that are appropriate should be brought to the patient’s notice.

Operation. Operation has an important place in treatment, but each operation must be considered as a component in the overall plan of management and not as a substitute for other measures. Operation may be applicable to the early stages of the disease, or it may be used in the later stages to salvage a joint that has been permanently damaged and remains a source of persistent pain.

In the early stages the operation most commonly used is synovectomy – excision of thickened and inflamed synovial membrane from joint or tendon sheath. As well as relieving pain, this may possibly slow down the inflammatory process and so help to preserve articular cartilage in an affected joint. It is undertaken mainly in the knee and wrist, and in the small joints and tendon sheaths of the hand.

Operation may also be required in the hand for repair or replacement of ruptured tendons, or for correction of finger deformities. In the painful elbow there is often a place for excision of the diseased radial head, and at the wrist excision of the lower end of the ulna may bring worthwhile relief in selected cases.

Operations used in the later stages of joint disease are arthroplasty and arthrodesis. Arthroplasty is applicable particularly to the hip and knee, and sometimes to the shoulder or elbow, and to the joints of the fingers and toes. Arthrodesis is usually the operation of choice for the joints of the spine, the wrist and the ankle.

Further details are given in the sections on individual joints.

JUVENILE CHRONIC ARTHRITIS (Juvenile rheumatoid arthritis; Still’s disease)

Juvenile chronic arthritis is uncommon. In the past the general term ‘Still’s disease’ was often used broadly to cover all its manifestations, but almost certainly the disease is not a single entity. Rather it comprises a number of conditions that are more or less distinct, though features common to all are pain, swelling and stiffness of joints. Recognised types include:

These subgroups vary in age of onset, sex incidence, course, complications, and prognosis.

Sero-positive juvenile rheumatoid arthritis is similar in all respects to the same disease in adults. It tends to begin rather late in childhood and affects girls more often than boys.

Classical Still’s disease begins in early childhood. In the systemic type there is swinging pyrexia with enlargement of lymph glands and of the spleen, with joint involvement simultaneously or later. The eventual outlook is favourable, as it is with the sero-negative polyarticular and pauciarticular variants – though the pauciarticular disease is complicated rather frequently by iridocyclitis necessitating local or systemic steroid therapy.

The sero-negative disease with sacro-iliitis is commoner in boys than in girls and tends not to begin until late in childhood: it may lead on to ankylosing spondylitis in early adult life. Most such patients show a positive test for HLA-B27 antigen and there is often clinical overlap between these patients and relatives with ankylosing spondylitis, Reiter’s disease, ulcerative colitis, or Crohn’s disease. It is thus probable that there is a hereditary factor in the causation.

Treatment. This is similar to that for rheumatoid arthritis in adults, with reliance on aspirin in the first instance and resort later if necessary to non-steroidal anti-inflammatory agents and possibly – in florid sero-positive disease – to gold therapy or penicillamine. Corticosteroid therapy should usually be avoided except for patients with iritis or iridocyclitis. General management includes adequate rest, temporary splinting of inflamed joints, graduated exercises with the physiotherapist, and occasionally operation – for instance, correction of fixed deformity or arthroplasty of the hip.

OSTEOARTHRITIS (Degenerative arthritis; arthrosis; osteoarthrosis; hypertrophic arthritis; post-traumatic arthritis)

Osteoarthritis is a degenerative wear-and-tear process occurring in joints. The joints may have been impaired by congenital defect, vascular insufficiency, or previous disease or injury. It is by far the commonest variety of arthritis.

Cause. It is caused by wear-and-tear that exceeds the capacity of the articular cartilage to renew and repair itself. If a joint were never put under stress it would never become osteoarthritic. Hence the relatively lightly stressed joints of the upper limb are, in general, less prone to osteoarthritis than the heavily stressed joints of the lower limb. Nearly always, however, there is a predisposing cause that accelerates the wear-and-tear process and there is now evidence that this may have a genetic basis. Almost any abnormality of a joint may be responsible, indirectly, for the development of osteoarthritis – often many years later. The main predisposing factors are:

Age alone is not a cause of osteoarthritis, though it may be associated with an impaired capacity for tissue repair after injury, and this may be an indirect causative factor.

Pathology. Any joint may be affected, the lower limb joints more often than the upper. The articular cartilage is slowly worn away until eventually the underlying bone is exposed (Fig. 9.3). This subchondral bone becomes hard and glossy (‘eburnation’), though it may also show the presence of degenerative cysts. Meanwhile the bone at the margins of the joint hypertrophies to form a rim of projecting spurs known as osteophytes. There is no primary change in the capsule or synovial membrane, but the recurrent strains to which an osteoarthritic joint is subject often lead to slight thickening and fibrosis.

Fig. 9.3 Osteoarthritis. The main changes are in the articular cartilage and underlying bone. The cartilage is gradually worn away, disappearing first at the points of greatest pressure. The subchondral bone becomes sclerotic, and at the joint margins it hypertrophies to form osteophytes.

Clinical features. Most patients with osteoarthritis are past middle age. When it occurs in younger patients there is usually a clear predisposing cause such as previous injury or disease of the joint. The onset is very gradual, with pain that increases almost imperceptibly over months and years. Movements slowly become more and more restricted. In some joints (notably the hip) deformity is a common feature in the later stages. This means that the joint cannot be placed in the neutral (anatomical) position.

On examination slight thickening is often found on palpation; it is mainly a bony thickening caused by the marginal osteophytes. There is no increased warmth. Movements are impaired slightly or markedly according to the degree of arthritis; in the larger joints movement is accompanied by palpable or audible crepitation of a rather coarse type. Fixed deformity (that is, inability of the joint to assume the neutral anatomical position) is often found in the hip, and sometimes at the knee and in other joints.

Radiographic features. The characteristic features of osteoarthritis are:

Fig. 9.4 A and B Radiographs of knee showing advanced osteoarthritis. There is marked joint space narrowing on the medial side and in the patello-femoral joint. Sclerosis of the sub-chondral bone and osteophyte formation at the joint margins are all typical features of osteoarthritis.

Diagnosis. This is usually made clear by the history, clinical findings, and radiographic features. Osteoarthritis is not easily confused with inflammatory forms of arthritis, because there is no synovial thickening, no increased local warmth, and no muscle spasm; radiographs show sclerosis rather than rarefaction, and the erythrocyte sedimentation rate is not increased.

Course. Osteoarthritis usually increases slowly year by year. In many cases the disability never reaches the stage at which treatment is required. In others increasing pain, stiffness, or deformity drives the patient to demand measures for its relief.

Treatment. The management of osteoarthritis exemplifies well the three categories of treatment that should be considered in every orthopaedic problem – namely:

In many cases treatment is not required. The patient may have sought advice only because of anxiety lest some grave disease be present. Reassurance, with advice to restrict excessive stresses on the affected joint with weight reduction where appropriate, is all that is required.

When more active treatment is called for, conservative measures should usually be tried first. The methods available include physiotherapy (often by local heat and muscle-strengthening exercises), analgesic drugs, supportive bandages or orthoses to normalise stresses, and, in selected cases, local (intra-articular) injections of hydrocortisone or hyaluronate. However, repeated steroid injections are of questionable benefit in osteoarthritis and may accelerate joint degeneration. In addition, the stress that is put upon the affected joint should be reduced – for instance, in the case of the joints of the lower limb, by restricting the amount of walking or by the use of a stick (cane) or crutch.

When severe disability, particularly rest or night pain and limitation of function, is unrelieved by conservative treatment, operation may be justified. Among the operations available are osteotomy to realign a joint; arthroplasty (the construction of a new joint) (p. 40); and arthrodesis (elimination of the joint by fusion) (p. 39). Osteotomy is useful mainly at the knee to correct varus or valgus deformity, and is occasionally used at the hip, but will only provide pain relief for a period of a few years. Arthroplasty has become the operation of choice in the majority of patients particularly when osteoarthritis affects the hip and knee, where it can provide good painless function in 95% of patients after 10–15 years. For a few joints, particularly in the hands and feet, arthrodesis may still be the operation of choice. Further details of treatment will be given in the sections on individual joints.

GOUTY ARTHRITIS (Podagra; urate crystal synovitis)

Gout is the clinical manifestation of a disturbed purine metabolism. It is characterised by deposition of uric acid salts – especially sodium biurate – in connective tissues such as cartilage (of joints, or of the ear), the walls of bursae, and ligaments.

Cause. The precise cause of the disturbance of metabolism is unknown. There is an inherited predisposition to the disease. In susceptible persons an attack may be induced by excessive consumption of purine-rich foods such as liver, kidneys, sweetbreads, shellfish, beer, or heavy wines. An attack may also be precipitated by recent injury or operation.

Pathology. The primary fault is an impaired excretion of uric acid by the kidneys. In consequence the level of urate in the plasma is increased, sometimes to 0.5 mmol/litre or more (normal = 0.1–0.4 mmol/litre (2.0–7.0 mg/100 ml)). In the blood the uric acid is in solution in a loose combination with proteins; it comes readily out of solution as a sodium salt (sodium biurate) to be deposited in the form of crystals in certain connective tissues, especially those that have been injured or those that have a sluggish blood supply, such as the articular cartilage of the joints of the foot. The deposited crystals set up an inflammatory reaction. In acute gout the deposit is microscopic in amount and is soon reabsorbed, with restoration of the tissue to normal. In chronic gout, however, widespread deposits of sodium biurate in joint cartilages, ligaments and the articular ends of bones lead to considerable disorganisation of affected joints. Gouty deposits, known as tophi, are also common at other sites, notably in the olecranon bursa and in the cartilage of the ear, where they may form prominent rounded nodules.

Clinical features. The patient is nearly always over 40, and is more likely to be a man than a woman, in the ratio of 10:1. The chief clinical manifestations are arthritis and bursitis.

Arthritis. Gout affects principally the peripheral joints such as the joints of the toes, tarsus, and ankle, and the small joints of the hands. It occurs in recurrent attacks. The first attack is usually in the great toe; later attacks may affect other joints. In an acute attack the onset is sudden – often during the night. The affected joint is swollen, red, and glossy. Pain is very severe. Movements are greatly restricted because of the pain. The attack subsides after a few days and the joint is normal between attacks.

In chronic gout several joints may be affected together. They are thickened and nodular, and painful on movement.

Bursitis. The bursa most commonly affected by gout is the olecranon bursa. It becomes distended with fluid, and there may be palpable deposits of uric acid salts.

Other manifestations. Deposits of uric acid salts (tophi) are common in the ear cartilages, where they form palpable nodules. Similar tophi may also occur at other sites.

Radiographic features. In acute attacks of articular gout the joints do not show any radiographic change. In chronic gout the deposits of uric acid salts in the bone ends show as clear-cut erosions adjacent to the articular surfaces, for the deposits are transradiant (Fig. 9.5).

Fig. 9.5 A and B Radiograph of finger showing gouty arthritis in the distal interphalangeal joint. There is marked soft tissue swelling from the deposit of urate crystals and well-defined ‘punched out’ juxta-articular erosions.

Investigations. There is sometimes a mild leucocytosis and the erythrocyte sedimentation rate may be increased. The plasma uric acid content is raised. Aspiration of swollen joints may yield a small quantity of turbid fluid, but never organisms. Polarised light microscopy of synovial fluid usually reveals needle-shaped crystals showing negative birefringence.

Diagnosis. Acute gout has to be distinguished from other forms of arthritis of acute onset, especially from acute pyogenic arthritis, acute ‘pseudogout’ (see below), haemophilic arthritis, and rheumatic fever. Features suggestive of gout are: a history of previous attacks, with symptom-free intervals; a raised plasma urate content; the presence of tophi in the ears or elsewhere; detection of crystals in synovial fluid; and a favourable response to treatment.

Chronic gout involving several joints may simulate rheumatoid arthritis.

Course. Gout usually occurs in recurrent acute attacks. Early attacks subside in a few days, leaving the joint clinically normal. In chronic gout the affected joints are gradually disorganised, and permanent disability is inevitable.

Treatment. For acute attacks reliance is usually placed upon a non-steroidal anti-inflammatory drug such as indometacin or naproxen. Colchicine is also effective. The affected joint should be rested until the attack has subsided. A large effusion in a major joint such as the knee should be aspirated and replaced by an instillation of hydrocortisone.

For patients with frequent attacks or with chronic gout, especially if the plasma urate level is persistently raised, long-term drug therapy to reduce the plasma urate level may be required. The two types of drug available are represented by:

Provided its long-term use is not associated with toxic reactions, allopurinol is probably to be preferred because it does not increase the load of urate in the urine, with its hazard of stone formation.

PYROPHOSPHATE ARTHROPATHY (Pseudogout)

With the general acceptance of the idea that joint manifestations in gout are caused by the presence of urate crystals, it has more recently come to be appreciated that similar manifestations may be induced by the crystals of other salts. In most such cases the crystals are composed of calcium pyrophosphate showing positive birefringence, and characteristically calcification of articular cartilage or of menisci is demonstrable radiologically (Fig. 9.6). Arthritis of this type has been termed ‘pseudogout’. It usually presents as a chronic arthritis with characteristic calcification of cartilage, but it may occur in an acute form mimicking a joint infection, from the shedding of crystals into the synovial fluid. The diagnosis can be confirmed by the finding of pyrophosphate crystals in the aspirated joint fluid. Treatment of an acute attack should be by rest, aspiration of joint fluid with intra-articular steroid injection, and a non-steroidal anti-inflammatory agent.

Fig 9.6 AP radiograph of knee with pseudogout or pyrophosphate arthropathy. There is a characteristic line of calcification within the joint space due to crystal deposition within the menisci and deeper layers of the articular cartilage.

HAEMOPHILIC ARTHRITIS

Joint manifestations are common in haemophilia, but examples are seen only infrequently because haemophilia is itself an uncommon disease.

Pathology. The term ‘haemophilia’ is used loosely to embrace a group of different defects in the process of coagulation of the blood. Classical haemophilia, the commonest of the group, occurs in males but is transmitted by females. There is an inherited deficiency of a specific clotting factor known as antihaemophilic factor (Factor VIII). In consequence the clotting time of the blood is prolonged and there is a tendency to undue bleeding, external or internal, when even quite small vessels are cut or torn. Joint manifestations are caused by haemorrhage into a joint, occurring after a minor strain or even without any known injury. The joints most commonly affected are those most vulnerable to strain – especially the knee, elbow, and ankle. The joint cavity is distended with blood (haemarthrosis), which is later slowly reabsorbed if the joint is rested. Recurrent haemarthroses lead eventually to degenerative changes in the articular cartilage and to fibrosis of the synovial membrane.

Clinical features. The patient, often a young boy, may be a known sufferer from haemophilia or can recall previous episodes of bleeding. He suddenly finds that a joint has become painful and swollen. On examination the findings vary according to the phase and duration of the arthritis. In the absence of specific treatment the joint remains swollen for several weeks after the acute onset – partly from effused blood and partly from the synovial thickening that results from interstitial extravasation. The overlying skin is abnormally warm. Joint movements are restricted and very painful.

In the quiescent phase between attacks of haemarthrosis there is moderate thickening of the joint from synovial fibrosis, movements are slightly impaired, and often there is some degree of fixed deformity – for instance, inability to straighten the knee fully.

Diagnosis. Because of the synovial thickening, increased warmth of the skin, and restriction of joint movements, haemophilic arthritis is easily mistaken for acute or chronic infective arthritis. The history of previous episodes of bleeding, the sudden onset, and the recurrent nature of the attacks are important diagnostic features: the prolonged clotting time of the blood is confirmatory evidence.

Imaging. In the later stages of the disease, particularly in those patients who have multiple bleeds from poor control of their clotting factor, the joints may show extensive surface erosions, juxta-articular bone cysts, with bone destruction and deformities (Fig. 9.7).

Fig. 9.7 AP and lateral radiograph of knee in chronic haemophiliac arthropathy. There are marked joint abnormalities in all three joint compartments with oversized epiphyses, build-up of osteophytes and reactive sclerosis.

Treatment. When the necessary facilities are available, the correct treatment for a recent acute incident is to promote coagulability of the blood by the administration of antihaemophilic factor in the form of Factor VIII concentrate or of cryoprecipitate, and then to treat the joint as for ordinary traumatic haemarthrosis by aspiration and temporary support in a plaster splint. Early treatment on these lines should reduce the incidence of irreversible fibrosis of the synovial membrane, hitherto a cause of serious permanent disability.

Failing adequate supplies of antihaemophilic factor, resort must be had to prolonged splintage.

In the chronic degenerative phase that follows repeated haemarthroses it is often necessary to give permanent support to the joint by means of a moulded plastic splint or other appliance. Operation must be avoided whenever possible, though it may if necessary be undertaken safely, provided that adequate cover by antihaemophilic factor can be provided.

The future outlook for haemophilic patients is much improved by the new-found ability to manufacture Factor VIII in commercial quantities by genetic engineering technology. If such a product can be developed to the point of being effective when taken by mouth the advantage will clearly be even greater.

NEUROPATHIC ARTHRITIS (Charcot’s osteoarthropathy)

In neuropathic arthritis a joint is disorganised by repeated minor injuries because it is insensitive to pain.

Cause. The underlying cause is a neurological disorder interfering with deep pain sensibility, although in a third of patients no demonstrable neurological deficit is present. In patients with involvement of joints of the lower limb the commonest cause in the past was tabes dorsalis, a manifestation of syphilis; but tabes is now uncommon, and there has been a corresponding decline in the incidence of neuropathic arthritis in the lower limb. Other causes are diabetic neuropathy, cauda equina lesion, and in some countries leprosy. In those with upper limb involvement the usual cause, apart from leprosy, is syringomyelia.

Pathology. Any of the large joints may be affected, including the joints of the spine. The knee, ankle, and subtalar joint are most commonly affected in the lower limb, and the elbow in the upper limb. In a normal joint harmful strains are prevented by a protective reflex whereby muscle contraction is evoked by incipient pain. When joint sensibility is destroyed the protective function of pain is lost. Strains are unrecognised and, cumulatively, they lead to severe degeneration of the joint. The changes may be regarded as a much exaggerated form of osteoarthritis. The articular cartilage and subchondral bone are worn away, but at the same time there is sometimes massive hypertrophy of bone at the joint margins. The ligaments become lax and the joint is unstable. Indeed it is often subluxated or even dislocated.

Clinical and radiographic features. The patient is usually in adult life. The main symptoms are swelling and instability of the affected joint. Since the joint is insensitive pain is slight or, sometimes, absent. On examination the joint is thickened, mostly from irregular hypertrophy of the bone ends. The range of movement is moderately restricted, and there is marked lateral laxity leading to instability. In extreme cases the joint may be dislocated. Further examination will reveal evidence of the underlying neurological disorder. Radiographs show severe disorganisation of the joint (Fig. 9.8). The changes are basically those of osteoarthritis, but enormously exaggerated. There is a loss of cartilage space and some absorption of the bone ends, often with considerable hypertrophy of bone at the joint margins.

Fig. 9.8 Neuropathic arthritis of the elbow. There is marked absorption of bone, with pathological dislocation. The underlying cause was syringomyelia.

Treatment. In most instances the best treatment is simply to provide support for the joint by a suitable appliance. Sometimes operation may be undertaken to fuse the joint, but fusion may be difficult to achieve. The primary neurological disorder will usually demand appropriate treatment.

ARTHRITIS OF RHEUMATIC FEVER

In adolescent children and young adults arthritic manifestations are a prominent feature of rheumatic fever. This has now become an uncommon disease in Western countries; so joint manifestations from this cause are hardly ever seen except in under-developed parts of the world.

Cause. Rheumatic fever is ascribed to a sensitivity reaction associated with infection by a haemolytic streptococcus. There may be an inherited predisposition to the disease.

Pathology. Any joint may be affected. The synovial membrane is acutely inflamed, but there is no suppuration. Clear fluid is effused into the joint.

Clinical features. The patient is usually a child over 10, or a young adult. There is constitutional illness, with malaise and pyrexia. A joint becomes painful and swollen, and soon afterwards other joints are likewise affected. On examination an affected joint is swollen, partly from contained fluid and partly from synovial thickening. The overlying skin is warmer than normal. Movements are markedly restricted, and painful if forced. Other features of rheumatic fever, such as carditis and chorea, should be looked for. Radiographs of affected joints do not show any alteration from the normal.

Investigations. There is a mild leucocytosis. The erythrocyte sedimentation rate is increased.

Diagnosis. Arthritis of rheumatic fever has to be distinguished from other forms of arthritis – especially from acute pyogenic arthritis, rheumatoid arthritis, gout, and haemophilic arthritis – and from acute osteomyelitis. Features suggestive of rheumatic fever are: onset in adolescence; affection of several joints together or in succession; severe pain with signs of acute inflammation, but without suppuration; a mild rather than a marked leucocytosis; a concomitant cardiac lesion; and a rapid favourable response to salicylates.

Treatment. For joint involvement alone salicylates are adequate, but prednisolone or a related steroid may be required if the heart is affected. A therapeutic course of penicillin should also be given to eliminate streptococci, and thereafter twice-daily oral penicillin should be continued well into adult life to reduce the risk of recurrent attacks.

ANKYLOSING SPONDYLITIS (Spondylitis ankylopoietica; Marie–Strümpell arthritis)

As the name implies, ankylosing spondylitis is primarily a disease of the spine, though in a few cases the arthritic changes involve also the proximal joints of the limbs, especially the hips. Briefly, it is a chronic inflammatory affection of the joints and ligaments of the spine, beginning in the sacro-iliac joints. It progresses slowly, the changes gradually creeping up the spinal column from below. The natural outcome is bony ankylosis of the affected joints (Fig. 9.9) but the disease may be arrested at any stage short of this.

Fig. 9.9 AP radiograph of sacroiliac joints in advanced ankylosing spondylitis showing typical complete fusion of the joints.

Typically, ankylosing spondylitis affects men in early adult life, with a strong hereditary link to the HLA-B27 gene. After remaining active for several years it tends eventually to become quiescent, always leaving some degree of permanent stiffness of the spine. A fuller description is given in Chapter 13 (p. 229).

CONGENITAL DISLOCATION OR SUBLUXATION

The most important representative of this group is congenital (developmental) dislocation of the hip (p. 343). Congenital club foot (talipes equino-varus) (p. 434) may be regarded as congenital subluxation of the talo-navicular joint. Congenital displacement of other joints is rare: an example that is seen occasionally is congenital dislocation of the head of the radius.

TRAUMATIC DISLOCATION OR SUBLUXATION

Injury is by far the commonest cause of dislocations. Traumatic dislocations are described in textbooks of fractures and joint injuries, and they will not be considered further here.

SPONTANEOUS (PATHOLOGICAL) DISLOCATION OR SUBLUXATION

Displacement may occur spontaneously at any joint in consequence of a structural defect or of destructive disease. It is encountered frequently in the spine, where the stability of the intervertebral joints may be impaired by structural defects, by previous injury, or by destructive arthritis (pyogenic, rheumatoid, or tuberculous). In the foot, it is common for a phalanx to become dislocated dorsally at the metatarso-phalangeal joint in cases of severe clawing of the toes; and in the hands interphalangeal subluxation may occur in rheumatoid arthritis. Another example is the dislocation of the hip that sometimes complicates severe tuberculous arthritis or pyogenic arthritis. Spontaneous subluxation or dislocation is also a common feature of neuropathic arthritis (p. 147).

RECURRENT DISLOCATION OR SUBLUXATION

Certain joints are liable to repeated dislocation or subluxation. Usually, but not always, there has been an initial violent dislocation which causes permanent damage to the ligaments or articular surfaces. The joints most often affected are the shoulder (p. 263), the patello-femoral joint (p. 409), and the ankle (p. 433).

INTERPOSITION OF SOFT TISSUE IN JOINTS

The smooth action of a joint may be obstructed by a displaced mass of soft tissue within it. The soft tissue most often responsible is an intra-articular fibrocartilage, especially a meniscus in the knee (p. 399). As a rule a fibrocartilage can be displaced only when it is torn. Other soft tissues that are occasionally interposed are synovial fringes and ligamentous tags.

Clinical features. Disorders of this type are common only in the knee. The characteristic features are recurrent sudden ‘locking’ or giving way of the joint, with later an effusion of clear fluid within it.

LOOSE BODIES IN JOINTS

Intra-articular loose bodies may be derived from bone, cartilage, or synovial membrane. They may be entirely free within the joint or they may retain a pedicle of soft tissue.

Causes. The commonest causes of loose bodies are:

Pathology. Osteochondritis dissecans (see below). The loose body is derived from a part of the articular surface that undergoes necrosis and separates.

Osteoarthritis. The bodies may be derived from marginal osteophytes, in which case they often retain firm soft-tissue attachments and may cause little trouble. Free bodies may be derived from shed flakes of articular cartilage: nourished by synovial fluid, these gradually enlarge.

Fracture of articular margin (osteochondral fracture). Fractures only occasionally cause intra-articular loose bodies. A well-recognised example is a fracture-separation of the medial epicondyle of the humerus, which may be sucked into the elbow joint while still retaining its muscle attachments.

Synovial chondromatosis (osteochondromatosis). This is a rare but well-recognised disease of synovial membrane. A large number of villous folds become pedunculated and their bulbous extremities undergo metaplasia to cartilage. Eventually they separate from their pedicles to become free mobile bodies, and many of them become calcified. The disease may affect any joint – or even the synovial lining of a bursa.

Clinical features. Loose bodies do not necessarily cause symptoms unless they become caught between the joint surfaces. In that event the characteristic feature is sudden painful but usually momentary locking of the joint, succeeded after some hours by an effusion of clear fluid within it.

Imaging. A radiograph of the affected joint will reveal the presence of multiple loose bodies, characteristically surrounding the margins of the articular surfaces (Fig. 9.11).

Fig. 9.11 AP radiograph of hip in synovial chondromatosis. There are multiple small calcified bodies within the distribution of the joint capsule.

Treatment. When a loose body causes trouble it should be removed. In synovial chondromatosis this may be combined with subtotal synovectomy.