126 patients with patellofemoral joint (PFJ) osteoarthritis (OA) were randomized to either a knee support brace, or a control group without brace support for 6 weeks. The purpose of this study was to determine the effects of a flexible knee brace on quadriceps maximum voluntary contraction (MVC) and athrogenous muscle inhibition (AMI) in PFJ OA patients. Patients in the control group were subjected to knee brace wearing after the initial 6 weeks. Knee brace wearing in all participants of the trial lasted for a duration of 12 weeks in the open-label phase of this trial. Findings indicated a significant decrease in AMI after 6 weeks in the brace wearing group compared to the control group, but no significant differences in MVC. All patients demonstrated significant improvements in MVC and AMI after 12 weeks of brace wearing in the open-label phase of the trial.