Level 2: Mid-level evidence
For moderate-to-severe secondary or idiopathic knee osteoarthritis, the addition of arthroscopic surgery appears no more effective than optimized physical and medical therapy alone, based on an unblinded randomized trial of 188 patients aged 18 years and older (N Engl J Med. 2008;359:1097-1107). There were multiple exclusion criteria: large meniscal tears, malalignment >5°, inflammatory or postinfectious arthritis, previous arthroscopy for knee osteoarthritis, Kellgren-Lawrence grade 4 osteoarthritis in two compartments in patients older than 60 years, intra-articular corticosteroid injection within three months, and previous major knee trauma. Patients were randomized to optimized physical and medical therapy with arthroscopic surgery vs. without arthroscopic surgery and followed for two years. Surgery consisted of debridement and lavage; optimal physical and medical therapy was based on an algorithm derived from American College of Rheumatology guidelines. Twenty patients (10.6%) withdrew consent or were lost to follow-up; five patients in the arthroscopy group declined surgery, but their data were analyzed as randomized.

The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score (2,400-point scale) at two-year follow-up; a decrease of 20% was considered clinically significant. Comparing arthroscopic surgery vs. control, mean total WOMAC score at baseline was 1,187 vs. 1,043 (P=.06). At two years, there were no significant differences between groups in mean total WOMAC score, quality-of-life scores, or other measures of pain and function. This trial supports the results of a previous trial that found arthroscopic debridement no more effective than arthroscopic lavage or placebo surgery (N Engl J Med. 2002;347:81-88).