None of the evidence we examined specifically included patients who had a primary diagnosis of meniscal tear, loose body, or other mechanical derangement, with concomitant diagnosis of osteoarthritis of the knee. The present recommendation does not apply to such patients. There were three studies that met the inclusion criteria for this recommendation. The Kirkley et al. and Kalunian et al. studies comparing arthroscopic lavage to placebo were rated as moderate strength and the Moseley et al. study comparing arthroscopic lavage to sham arthroscopic surgery was rated as high strength. Kirkley et al. reported that a large number of patients were not eligible for participation in their study (38%) largely due to the exclusion criteria of substantial knee malalignment. In some cases, patients declined participation. Kirkley et al. compared arthroscopic surgery to lavage and debridement combined with usual physical therapy and medical treatment, usual care. The authors used the pain, functional status, and other symptoms subscales of the Arthritis Self-Efficacy Scale and the McMaster-Toronto Arthritis Patient Preference Disability Questionnaire at multiple time points (ranging from three months to two years). Out of 20 outcomes, only two were statistically significant in favor of surgery with lavage. Differences in Arthritis Impact Measurement Scales pain scores were statistically significant at three months and differences in Arthritis Impact Measurement Scales-Other Arthritis Symptoms subscale scores remained significant after two years. In summary, this randomized controlled trial demonstrated no benefit of arthroscopic surgery compared to physical therapy and medical treatment for osteoarthritis of the knee. Kalunian et al. included a large number of enrolled patients from one institution with intraarticular crystals in their knee. They compared arthroscopic lavage with 3,000 mL saline to lavage with 250 mL saline. There were not any statistically significant differences in visual analog scale and Western Ontario and McMaster Universities Osteoarthritis Index pain scores between the two treatment groups. The Moseley et al. study raised questions regarding its limited sampling (mostly male veterans) as well as the number of potential study participants who declined randomization into a treatment group. In this randomized controlled trial, the effects of arthroscopy with debridement or lavage were not statistically significant in the vast majority of patient-oriented outcome measures for pain and function, at multiple time points from one week to two years following surgery. Collectively, the three included studies did not demonstrate clinical benefit of arthroscopic debridement or lavage. The work group also considered the potential risks to patients (anesthesia intolerance, infection, and venous thrombosis) associated with surgical intervention. It was agreed that the lack of evidence for treatment benefit and increased risks from surgery were sufficient reasons to recommend against arthroscopic debridement and/or lavage in patients with a primary diagnosis of osteoarthritis of the knee.