The timing of arthroscopic partial meniscectomy (APM) is not well defined. The purpose of this study was to evaluate the impact of early surgical intervention on the short-term improvement in clinical outcome. Between June 2012 and July 2013, patients who had APM for symptomatic irreparable meniscal tears in stable knees with no preoperative radiographic osteoarthrosis were included (n = 187). The mean age was 45.6 ± 14.5 years. Early surgical intervention (duration of symptoms of less than 3 months) was evaluated together with various preoperative and operative variables in a multivariable stepwise regression analysis, while the improvement in Lysholm knee score was modeled as a function of these predictors. At the last follow-up, the mean Lysholm knee score improved by 14.7 points and 79% of all patients declared they were satisfied to have had the operation; however, of the various predictors in the regression analysis, patients who had shorter duration of symptoms or better clinical function before surgical intervention had greater improvement in clinical score. In conclusion, early APM for symptomatic irreparable tears in stable knees without preoperative arthrosis had better improvement in clinical results than in delayed intervention.