The purpose of this study was to determine functional and radiographic changes on long-term followup of knees with isolated meniscal tears. Sixty-seven patients were evaluated retrospectively with an average of 12.2 years' followup using the scale of Tapper and Hoover. The criteria for the radiographic results were the Fairbank's changes as the standard comparing the preoperative and the postoperative conditions of the affected knee with the contralateral knee. Seventy-nine percent of the patients had a satisfactory outcome in terms of function. The amount of meniscus removed and the Outerbridge classification of the articular cartilage at the time of the meniscectomy were determining factors for long-term functional results. Osteoarthritic deterioration was seen in 48% of patients after the surgery, but radiographic deterioration after arthroscopic partial meniscectomy was mild on long-term followup. Medial meniscectomy and the amount of meniscus removed were risk factors for postoperative radiographic change. Age, gender, and the degree of cartilage degeneration at the time of operation, in contrast, showed no significant association. Arthroscopic partial meniscectomy for isolated meniscal injury yields favorable functional results but leads to significantly increased osteoarthritic change in the long-term.