To investigate whether changes from 2 to 4 years post arthroscopic partial meniscectomy (APM) in mechanical muscle function and objectively measured function differ between the operated and contra-lateral leg of APM patients or compared with controls.Twenty-two patients (age 46.6 ± 5.0, BMI 24.7 ± 2.9) and 25 controls (age 46.4 ± 5.2, BMI 25.1 ± 4.6) previously examined at ~2 years post APM were examined again at ~4 years post surgery for maximal knee extensor/flexor voluntary contraction (MVC) and rapid force capacity. Functional performance was assessed by the distance achieved during a one-leg hop test and the maximum number of knee bends performed in 30 s. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was used to evaluate self-reported outcomes.Overall changes from 2 to 4 years post APM did not differ in maximal muscle strength, rapid force capacity, and functional performance between the operated and contra-lateral leg of patients or control legs. However, secondary analysis showed a difference in change in knee extensor MVC resulting in a 6% difference between the operated and contra-lateral leg of patients at follow-up.No differences in longitudinal changes were observed from 2 to 4 years post APM between patients and controls. The secondary finding of differential changes over time in knee extensor MVC between the operated and contra-lateral leg partly confirm our hypothesis that differences in muscle strength may evolve from 2 to 4 years post APM. This differential change may represent an initial sign of an evolving lower limb muscle asymmetry, which may play a role in the development of knee OA.III.