Meniscectomy is recognized as an important risk factor for the development of knee osteoarthritis (OA), a disease that traditionally has been considered as a simple "wear and tear" phenomenon. However, despite numerous reports, little evidence has been presented that a limited meniscal resection, compared with a more extensive resection, reduces the risk of OA by preserving meniscal function. Why? This thesis provides one possible answer to that question. Patients, who had undergone isolated meniscal resection in 1973, 1978, or between 1983 and 1985 at Lund University Hospital, Sweden, were reviewed clinically and radiographically 15-22 years after the surgical procedure. Of the subjects (n = 317) almost 50% had developed radiographic OA in their operated knee, but just over half of these patients were symptomatic. An additional 20% of the patients had knee symptoms, but did not have radiographic knee OA. These results confirm a limited correlation between radiographic features of the disorder and symptoms. A degenerative type of meniscal tear and obesity were the factors most strongly associated with both radiographic knee OA and symptomatic radiographic knee OA. Partial meniscal resection induced less radiographic changes related to knee OA compared with total meniscectomy, but the patient-relevant outcomes remained essentially the same. If radiographic hand OA was present there was an increased likelihood of the patient also having knee OA following meniscectomy. This finding was independent of age, and therefore an inherited susceptibility to the disease contributes to the risk of knee OA after meniscal tear. Genetic and environmental risk factors interact in OA development. A degenerative meniscal lesion is often associated with early-stage knee OA, a disorder also involving the meniscal tissue. The tear may thus represent the first "signal" feature of OA. The challenge for the health professional is to discriminate between symptoms caused by a meniscal tear and those caused by OA. Meniscal resection may not benefit the patient with early-stage knee OA. The intervention merely removes evidence of the disorder, while the OA joint degradation proceeds.