We found one good quality randomised controlled trial that was directly relevant to the question. It found that arthroscopic debridement and lavage did not improve pain and function compared with placebo in people with knee osteoarthritis. We found limited evidence that full arthroscopic lavage improves pain compared with low volume lavage in people with mild knee osteoarthritis. We found limited evidence that arthroscopic debridement improves pain compared with arthroscopic lavage in people with osteoarthritis of the medial femoral condyle only. We found no evidence that arthroscopic lavage or debridement improves patient reported pain, function or disability compared with non-arthroscopic treatments.