[Knee pain in the aged--pathomechanism, diagnosis, and treatment of osteoarthritis of the knee].

Osteoarthritis is the most common cause of knee pain in the aged. This disease is characterized by degenerative changes in the articular cartilage and subsequent new bone formation at the articular margins. The primary defect in hyaline cartilage is an alteration in the ratio of total glycosaminoglycans to that of the collagen fiber content in the matrix. The disease frequently is primary but various predisposing conditions are recognized. In early phase of this disease, the patient complains of pain, which appears with exercise but can be "walked off". The joint is often felt to creak and grate, and swells from time to time, especially after any unusual activity involving a flexed position. As the disease progresses, the patient finds increasing difficulty in the activities of daily life. It should be emphasized that, in the early phase, almost of all patients can be managed by conservative means such as weight loss, isometric quadriceps exercises, use of a walking stick and antiinflammatory analgesic drugs. The predominant indication for surgical treatment is persistent pain and serious disturbance of the activities of daily life against conservative treatment. High tibial osteotomy has proved to be useful in the medial osteoarthritic knees. However, the long-term follow-up studies conducted by the author have shown that effects of this procedure gradually deteriorate after 10 years. Clinical results of total prosthetic replacement of the knee joint have been well improved in this decade. Ten-year survivorship has recently been reported to be 95% or more. However, the most common problem is loosening of the component. Wear particles derived from the tibial plate made from ultra high molecular weight polyethylene have been noted as the primary cause of the loosening.