The knee is very susceptible to problems, especially from sports such as football and skiing, where the body turns fast on a fixed foot. The history will give a clue to the structures likely to be damaged. The key to rehabilitation of problems with the knee is physiotherapy, as the quadriceps muscle wastes very quickly if the knee has been injured. Control of knee movements is lost, and the knee is then susceptible to a secondary injury such as a tear of the meniscus. Patients with injured knees should not return to sport until the muscle has recovered. A simple test for this is to ask the athlete to run as fast as they can – backwards – in a figure of eight (‘figure of eight’ test). If the knee feels unstable to the athlete, more work is needed before they are safe to return to sport.

Locking and pseudo-locking

• Locking is the sensation that a patient gets when walking along and quite suddenly the knee will not straighten. The patient may end up sitting in the road jiggling the knee until the mechanical block clears from the knee. This is characteristic of a torn meniscus or of a loose body jamming in the knee.
  
• Pseudo-locking occurs in a knee which is inflamed, when the knee is first moved after a period of stillness. This first movement causes such severe pain that the patient cannot move it further, until the inflamed layers of synovium that have stuck together are freed up. Pseudo-locking occurs commonly in teenage children, especially girls, and is associated with pain in the front of the knee and great difficulty on stairs especially descending. This anterior inflammation of the knee is sometimes called chondromalacia patellae (a beautiful but meaningless name) and usually resolves spontaneously.

Patella apprehension

Hypermobile patients are liable to dislocate the knee cap laterally. Once this occurs, any attempt to reproduce the dislocation (by pushing the knee cap laterally, as the knee is flexed) produces an ‘impending sense of doom’ in the patient similar to the shoulder apprehension sign (see Chapter 6).

Anterior cruciate tear

The anterior cruciate ligament stops the tibia sliding forward and rotating on the femur. It is torn by a twisting injury on a bent knee. The ligament has no blood supply and so cannot heal. If the quadriceps cannot be built up enough to control the knee, then the patient will find the knee giving way when they twist or turn on it. The abnormal movement in the knee often leads to a tear of the menisci as well, causing true locking. The torn menisci need repairing or trimming through the arthroscope, and if the patient cannot cope with the instability even after intensive physiotherapy, then a substitute anterior cruciate ligament may need to be inserted, followed by a long course of rebuilding strength and proprioception around the knee.

Arthritis in the knee

This is as common in the elderly as arthritis of the hip. The patient gets pain at the end of the day and at night. There may be a lump at the back of the knee (Baker’s cyst) – an outpouching of the excess synovial fluid. Total knee replacements can now give as reliable results as hip replacements, lasting 10–15 years before wearing out and needing changing. Osteoarthritis normally starts in the medial tibiofemoral joint so there are sometimes indications for a unicompartmental knee replacement (just one-half of the joint).

Gastrocnemius tear

This sports injury can mimic a deep vein thrombosis (apart from the history of onset) as it profuces a painful red and swollen calf. It heals with conservative management: Painkillers and anti-inflammatories, Rest, Ice, Compression, and Elevation (PRICE).

Ruptured tendo Achilles

See Chapter 20.

Instability

Chronic instability of the ankle can arise after a torn ligament fails to heal. Surgical repair with a substitute ligament, followed by intensive physiotherapy, should offer reasonable results, but requires a positive input from the patient too.

Arthritis of the ankle

This is common after trauma involving the ankle and in patients with inflammatory joint disease. Ankles are best fused if there is osteoarthritis or arthritis secondary to trauma, as ankle replacements tend not to do well in these conditions. However ankle replacements do well in patients with inflammatory joint disease and are especially useful because other joints around the ankle affected by the same disease are likely to be stiff.

Hallux valgus/bunions

These are very common especially in people with wide feet who try to wear narrow shoes. The big toe bends laterally (hallux valgus) leaving a prominent head of the metatarsal bone which forms a bursa over it while the skin becomes inflamed. Surgery is designed to narrow the foot with an osteotomy through the metatarsal, while at the same time the bunion itself is removed and the toe straightened.

Claw toes, hammer toes and metatarsalgia

• Inflammatory joint disease in the feet causes dorsal dislocation of the metatarsal phalangeal joints with clawing of the toes. The metatarsal heads become very tender to walk on. Patients often describe a feeling as of walking barefoot over pebbles (metatarsalgia). Operations to straighten the toes and bring a thick pad of tissue over the metatarsal heads, combined with properly padded shoes, can make walking much more comfortable.
  
• Hammer toes result from spasm, then contracture of the intrinsic muscles of the foot.
  
• Patients with rheumatoid arthritis are especially susceptible to problems in the feet because of the disease’s affinity for the small joints in the hand and foot.

Flat feet

Some people have a high arch to the foot, others a lower one, but true flat foot is a failure of the foot to form an arch when the patient stands on their toes (the windlass test). It can be caused by congenital tarsal coalition (bones fused from birth) or occurs in patients with inflammatory arthritis where the ligaments supporting the arch have stretched out. Pathological flat feet are difficult to treat either non-operatively with special shoes or surgically with tendon transfers or joint fusion operations.