The causes of persistent symptoms after meniscectomy have been assessed clinically, radiologically and arthroscopically in 174 knees. The commonest finding was early degenerative arthritis (chondromalacia) of the femoral condyle (40 per cent). Retained fragments of meniscus were less common than expected (13 per cent), and lesions of the other meniscus were rare (5 per cent). The clinical diagnosis was altered in 42 per cent by arthroscopic examination. Arthroscopy was found to be a valuable technique in this group of patients with problems of diagnosis.

A study has been made of 800 consecutive arthroscopic examinations of the knee with special emphasis on the changes in management that resulted. Of 614 knees that would have been operated upon if arthroscopy had not been available, open operation was avoided in 32 per cent, a different operation was done or planned in 27 per cent, and there was no important change in the remaining 41 per cent. Of 186 knees that would have been treated conservatively if arthroscopy had not been available, the examination resulted in some immediate benefit to 30 per cent of the patients. There were no wound infections after arthroscopy alone, and the known incidence of incorrect interpretation was 1.4 per cent.

1. A critical analysis of the findings in 200 knees examined by arthroscopy at least one year previously has been carried out to assess its value in the management of a wide variety of disorders.

2. Arthroscopy is a practical and valuable procedure with minimal associated morbidity or complications.

3. The increased accuracy of diagnosis helps to avoid unnecessary operations and to base methods of treatment on a better knowledge of the pathology.