Disorders of joints

As mentioned above, the articular cartilage has no blood supply. It is nourished by the synovial fluid, the nutrients being produced by the synovial membrane. The nutrients diffuse through the joint, speeded by the movement of that joint.

  Osteoarthritis (Fig. 26.1)

This is the common pathway for all diseases which damage the articular cartilage. The patient complains initially of pain on movement, and over a period the joint becomes stiffer and stiffer, gradually fixing in the position of maximum comfort. The muscles around the joint tend to waste and weakness sets in, further hampering the patient’s mobility.

Eventually the joint may actually collapse, the limb shortens and the joint may lose its normal alignment.

Examination

On inspection the joint may be slightly red and there may be swelling of the soft tissues, combined with muscle wasting. The limb is held in the position of comfort and may even be deformed. There may be some heat over the joint, and careful examination usually reveals at least a small effusion (although it can be very large). The osteophytes around the joint may be palpable and the joint line itself is often tender to palpation. Movement will be markedly limited and crepitus may be both palpable and audible. In osteoarthritis, the knee tends to fall into varus (bow legs), while in rheumatoid arthritis the knee falls into valgus (knock knees). The hip tends to flex into internal rotation, and the limb may actually shorten if there is bone loss.

Treatment

The early treatment of osteoarthritis is aimed at treating the pain and disability. Nonsteroidal anti-inflammatories may help with the pain. Physiotherapy should help to maintain mobility. It is said by some that weight loss improves symptoms. Walking sticks and household aids including a seat in the shower and handles around bathroom fittings may help the patient to maintain independent existence.

Once these nonoperative measures are no longer adequate, joint replacement should be considered in the hip, knee and the shoulder, as replacement in these joints now has good long-term results. Even so, in a young active patient, an arthrodesis should always be considered as an alternative. It is strong. It should give complete pain relief and can always be taken down and replaced with an artificial joint if necessary. Arthrodesis should only be considered when a single joint is affected, otherwise it transfers extra load on to already compromised joints.

Aetiology

Primary osteoarthritis develops spontaneously without any apparent predisposing cause.

Secondary osteoarthritis. This is the final common path­way after damage to the joint from some other cause. This may be traumatic, sepsis or inflammatory arthritis. Even repeated bleeds into a joint (as occurs in haemophilia) will cause breakdown of the articular cartilage, and multiple attacks of gout or pseudogout will have the same effects.

Underlying pathology of osteoarthritis

Articular cartilage is a complex structure made up of collagen and proteoglycan molecules which are highly hydrophilic and create the turgor pressure of the articular cartilage which gives it its strength and resilience. The joint surface itself is lubricated by a film of fluid squeezed out of the articular cartilage by the pressure applied. The first signs of osteo­arthritis appear to be some softening of the articular cartilage (or at least loss of this turgor pressure) followed by a break­down in the smooth surface. Microcracks appear in the articular surface (fibrillation) and pieces of the articular carti­lage start to break off. These small fragments are mopped up by the macrophages in the synovium but this produces an inflammatory response. At the same time it appears that some form of repair mechanism is going on. This repair mechanism does not seem able to replace the articular cartilage in the load-bearing area of the joint. Instead, there is new bone formation and fibrocartilage laid down around the edge of the joint. This ring of new bone may be visible on the X-ray as osteophytes. The bone arcades lying immediately beneath the articular cartilage and which supported it now become more sclerotic, perhaps because of the increasing load coming on to the bone. The synovial fluid appears to break through the cartilage to create cysts in the subchondral bone. Finally the articular cartilage is completely worn away (eburnation) and there is direct articulation bone to bone. Pain may serve a protective function because in those joints lacking pain perception (Charcot’s joints) the disintegration of the joint is both more rapid and more severe. Eventually the bone itself breaks down and the joint collapses completely.

Cardinal features of osteoarthritis on X-ray

These include:

   loss of joint space;

   subchondral sclerosis;

   osteophytes;

   cysts.

Radiological features of osteoarthritis (Fig. 26.2).

These include:

  joint narrowing;

 osteophyte formation;

  subchrondral sclerosis;

cyst formation.

Rheumatoid arthritis

This is much rarer than osteoarthritis and occurs in a younger age group. Indeed, it can occur in children, when it is called Still’s disease. The disease is usually symmetrical and starts in the small joints of the hands and feet. Women are more commonly affected than men. As each joint becomes involved, it becomes red, stiff and painful. After a time the disease burns out in an individual joint, but the damage is done and secondary osteoarthritis now sets in.

History

Characteristically the patient complains of feeling generally unwell and the painful joints are most painful and stiff early in the morning when the patient first gets up. This is in con­trast to osteoarthritis where the joint is usually most painful in the evening after a long day’s activity.

Examination

The skin over the joints is red and glassy. The soft tissues are swollen and in the late stages the joints may be subluxed or even dislocated. The skin may be hot to touch and the swell­ing of the soft tissues is often as much synovial thickening as a synovial effusion. The joint therefore feels doughy rather than having a simple effusion. The bones do not usually have palpable osteophytes. Normal movement is markedly dimin­ished but the joint may be grossly unstable as the ligaments around the joint may have stretched, or the joint surface itself may have collapsed.

Treatment

The bulk of treatment for rheumatoid arthritis is nonopera­tive. Nonsteroidal anti-inflammatories, analgesics and immunosuppressants, including steroids, are routinely used, combined with splints and with physiotherapy. If these mea­sures fail then surgery needs to be considered. In the early stages where there is massive synovitis but relatively little damage to the articular cartilage as yet, a synovectomy may slow the course of the disease and reduce damage to liga­ments and tendons. However, the procedure is not easy to perform and the results are not impressive. Once the joint surface has been destroyed then joint replacement may be the only option. Arthrodesis does not work well in rheumatoid arthritis as the bone is soft and other local joints are involved by disease. Paradoxically, joint replacement works well in rheumatoid arthritis and can be used in the hip, knee, shoulder, elbow and even the metatarsal phalangeal joints. However, fusion of the wrist remains the best solution for severe rheumatoid arthritis of this joint.

Pathology

A pannus of inflammatory tissue spreads from the margin of the joint, across the articular cartilage, creating inflammation in the joint and destroying the articular cartilage. The bone around the joint becomes osteoporotic, possibly because of hyperaemia, and because of disuse. In the late stages the joint may collapse completely.

Charcot’s joints neuropathic joints

Any joint which has lost its nerve supply seems to he susceptible to a particularly aggressive form of arthritis. The condition was originally described with tertiary syphilis but can in fact occur whenever the sensory supply to a joint is affected. There is massive joint destruction combined with new bone formation producing a very disorganised joint in a patient who is complaining of surprising little pain. Once seen it is never forgotten.

Nonspecific seronegative arthritis

Not all arthritis is either osteoarthritis or rheumatoid arthritis. Acute onset of pain in joints can occur secondary to a viral infection or indeed for no known cause. The treatment is symptomatic with anti-inflammatories, splints and physiotherapy.

Chondromalacia patellae anterior knee pain

This condition occurs in adolescents, particularly girls, and may initially be brought on by a blow to the knee. The patient complains of severe pain in the knee which is worse going down stairs and if they are obliged to sit still for any length of time. After this period of rest any attempt to move the knee is extremely painful and may cause them to collapse. On examination there is surprisingly little to see. There is no redness or swelling and there may be very little thickening of the synovium and no effusion. Range of movement is good but there may be crepitus from the patella. The synovium around the patella is tender to palpation.

This condition can also be caused by maltracking of the patella but in the majority of cases there is no obvious cause to be found.

Luckily, the condition is usually self-limiting and treatment is symptomatic using nonsteroidal anti-inflammatories, splints and physiotherapy and trying to keep the patient as mobile as possible within the limits of pain.