Frequently, meniscal pathology accompanies degenerative changes affecting the articular surface of the knee. The attritional changes in the meniscus lead to fragmentation of the meniscus and a variety of tears, usually of the posterior horn of the medial meniscus. A prospective study of the results of arthroscopic partial meniscectomy in the presence of at least Outerbridge Grade III chondromalacia of the accompanying joint surface was performed between 1980 and 1984. Eighty-seven knees in 84 patients were studied. The mean age was 62 (29-84) years. The right knee was involved in 44 patients, and 47 were men. Preoperative radiographs demonstrated osteoarthritis in 53 patients. The medial meniscus was involved in 82, while the lateral meniscus was affected in nine knees. Four knees had involvement of both menisci. In 72 knees, the most frequent lesion was a tear of the posterior horn of the medial meniscus. The most frequent configuration of the tears was a flap in 42. The morbidity was small with the use of ambulatory aids being 10 +/- 13 (mean +/- SD) days. Subsequent surgery was performed on six knees consisting of two total knee arthroplasties, two upper-tibial osteotomies, one repeat arthroscopic meniscectomy, and one popliteal cyst excision. Two patients had poor results related to progression of their arthritis and one developed osteonecrosis. Five patients were unchanged from their preoperative status. Subchondral sclerosis or osteophytes on the preoperative radiographs correlated with 72% compared to 90% satisfactory results in the absence of these findings (p less than 0.03). Complications consisted of superficial thrombophlebitis in three, hemarthrosis in one, and superficial infection in one patient.(ABSTRACT TRUNCATED AT 250 WORDS)