It is usually a football injury, but is common among men who work in a squatting position. The medial meniscus is torn much more often than the lateral.
Late effects – long continued internal derangement from a torn meniscus predisposes to the later development of degenerative arthritis.
Cysts of the Menisci – a cyst of the meniscus (semilunar cartilage) forms a tense solid swelling at the level of the joint, usually on the lateral side; cysts arise spontaneously, but there is often a previous history of direct injury at the site of the cyst.
Anterior knee pain (chondromalacia of the patella)
Anterior knee pain is a generic term that almost certainly includes more than a single clinical entity. The clinical syndrome occurs in adolescents, especially girls. In chondromalacia of the patella the cartilage of the articular surface of the patella is roughened and fibrillated for reasons that are unknown. Clinical features – the patient is often a girl aged between 15 and 18 years. There is aching and pain deep in the knee, behind the patella. There is often effusion of fluid and tenderness may be found on palpating the surface of the patella after displacing it to one side.
Osteochondritis Dissecans of the knee
Cause – It has been suggested it is caused by impairment of the blood supply to the affected segment of bone by thrombosis of an end-artery but injury is possibly a predisposing factor.
Loose bodies in the knee
The knee is the joint most commonly affected by the formation of loose bodies. There are four main causes:
- Osteoarthritis (1-10 loose bodies)
- Osteochondritis dissecans (1-3 loose bodies)
- Chip fracture of a joint surfaced (1-3 loose bodies)
- Synovial chondromatosis (50-500 loose bodies)
Clinical features - the characteristic symptom of a loose body in the knee is recurrent locking of the joint from interposition of the loose piece between the joint surfaces. Suddenly without warning the knee becomes jammed during movement. Locking is accompanied by severe pain. The following day the knee is found to be swollen with fluid.
Recurrent dislocation of the patella
The patello-femoral joint is one the three joints that are most liable to recurrent displacement, the others being the shoulder and the ankle. Recurrent dislocation of the patella is more common in girls and trouble normally begins in adolescence. The dislocations occur while the patient is engaged in some activity that entails flexing the knees. Treatment – after a dislocation the patient should receive a course of physiotherapy designed to strengthen the quadriceps muscle and especially the vastus medialis. If dislocations recur with such frequency that the patient is seriously disabled, operation should be advised.