The knee

Chronic knee pain is common at all ages, particularly in the elderly, among whom it has its greatest impact. Chronic knee pain is often ascribed to osteoarthritis in adults and to chondromalacia patellae in children and adolescents. Pathological findings in both these conditions correlate poorly, however, with the severity of knee pain and disability. Psychometric variables correlate better with the impact of knee osteoarthritis, suggesting that this disorder has characteristics of a regional pain syndrome. This perception may reflect our lack of understanding of the biological mechanisms in these disorders. This possibility has been highlighted by the advent of magnetic resonance imaging, and by recent studies of muscle function, reflex quadriceps inhibition and proprioception in people with knee osteoarthritis. Established risk factors for knee osteoarthritis include increased body weight, knee injury and aspects of occupational activity. Recent studies have also suggested a possible role for oestrogens and vitamins C and D in the secondary prevention of this disorder. The emergence of 'nutraceuticals' such as glucosamine as treatments for osteoarthritis has captured the public imagination and merits further study.