Background Knee muscle weakness and a greater external knee adduction moment are suggested risk factors for medial tibiofemoral knee osteoarthritis. Knee muscle weakness and a greater knee adduction moment may be related to each other, are potentially modifiable, and have been observed after arthroscopic partial meniscectomy. Questions/purposes The aim of this exploratory study was to determine if knee muscle weakness 3 months after arthroscopic partial meniscectomy (baseline) is associated with an increase in external knee adduction parameters during the subsequent 2 years. Methods Eighty-two participants undergoing medial arthroscopic partial meniscectomy were assessed at baseline, and 66 participants who were reassessed 2 years later were included in our study. Isokinetic muscle strength and external adduction moment parameters (peak and impulse) during normal and fast walking were measured at baseline and followup. Multiple linear regression models were used to examine the association between baseline muscle strength and 2-year change in adduction moment parameters. A post hoc power calculation showed we had 80% power to detect a correlation of 0.31 between baseline muscle strength and change in the external knee adduction, with an alpha error of 0.05 and two-sided significance. Results Maximal isokinetic muscle strength 3 months after arthroscopic partial meniscectomy was not associated with change in adduction moment parameters (p value range from 0.12 to 0.96). Conclusions No evidence was found to suggest that improving maximal knee muscle strength after a recent arthroscopic partial meniscectomy would reduce change in knee adduction moment observed during the subsequent 2 years. As muscle function is modifiable, future investigation of other aspects of muscle function that may relate to change in knee adduction moment is warranted. Level of Evidence Level II, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.