Arthroscopic debridement was carried out in 49 knees of 44 patients. These patients, who had a primary diagnosis of arthritis, were older than 50 years of age. Two-thirds had roentgenographic evidence of severe arthritis. Age, weight, compartment location of arthritis, and presurgical range of motion did not affect surgical results. Symptoms of long duration, arthritic severity as evidenced by roentgenograms, and malalignment predicted poor results. Conversely, shorter duration of symptoms, mechanical symptoms, mild to moderate roentgenographic changes, and crystal deposition correlated with improved results. Surgery offered no benefit for 39% of the patients. Another 9% had temporary improvement, averaging 15 months, but were judged failures at the final follow-up examination. Good or excellent results were achieved in 52% of the patients and maintained through the final follow-up examination in 40% of the patients. Of these, two-thirds had no visible deterioration within a 33-month average follow-up period.