BACKGROUND: Most meniscus lesions are of non-traumatic origin. The indications for partial meniscectomy are controversial. METHODS: We systematically searched the literature for randomized controlled trials (RCTs) comparing partial meniscectomy with non-surgical treatment. RESULTS: Of 6870 articles retrieved by the literature search, we were able to include six in this systematic review. Five trials showed no difference between the clinical outcomes of patients who underwent arthroscopic partial meniscectomy and those who underwent control treatment (arthroscopic lavage, physiotherapy, glucocorticoids). In three trials, however, symptoms improved in 21-30% of the patients in the physiotherapy group only after they underwent arthroscopic partial meniscectomy (crossover design). In two trials, the percentage of patients who crossed over from one treatment arm to the other was markedly lower; in one, the frequency of crossing over was not reported. In one RCT, the patients who underwent arthroscopic partial meniscectomy had significantly less pain and other symptoms. Five of the six trials had acceptable scores for method, but all had weaknesses. These mainly concerned the description of the surgical techniques and the failure to take account of analgesic use-in particular, the use of non-steroidal antiinflammatory drugs (NSAIDs). CONCLUSION: For most patients with non-traumatic meniscus lesions, surgical and non-surgical treatments seem to be of equal value; only one of the six included trials revealed lower pain and symptom scores after arthroscopic partial meniscectomy. In multiple trials, however, the crossover analysis showed that non-surgical treatment fails for some patients. These patients may benefit from arthroscopic partial meniscectomy. Further trials are needed to better define this subgroup of patients.