BACKGROUND Osteoarthritis knee (OA) for patients whom had varus malalignment had higher peak adductor moment. Hip abductor strength played an important role in the decreasement of knee adduction moment. This study aimed to evaluate the effect of hip abductor exercises for patients who had medial compartment knees OA. METHODS Patients who had medial compartmental OA knee were randomized into two groups. The first group performed hip abductor strengthening exercises, combined with quadriceps strengthening exercises; whereas, the second group performed standalone quadriceps strengthening exercises. Self-reported Knee Injury and Osteoarthritis Outcome Scores (KOOS) were collected by patients on follow-up visits. RESULTS Eighty-six patients completed the trial. All KOOS subscales were significantly improved in both groups after 10 weeks of treatment. However, there was no significant difference in the scores between either group at 2-10 weeks after treatment. Nevertheless, the effects of exercise for pain, symptoms, function in daily living and knee-related quality of life were found to have faster improvement within the hip abduction exercise group compared to the control group (2 weeks faster; pain, function in daily living and knee-related quality of life, 4 weeks faster; symptoms.) CONCLUSION: Since, adding quadriceps exercises could expedite improvement of less pain, symptoms, activity in daily living and quality of life faster than quadriceps exercises solely for a 2-4 weeks period. However, the effect size was small and there were no differences after this; hence, consideration of adding hip abductor exercises in the treatment protocol should be based on the patients and doctors appraisal. BACKGROUND TCTR, TCTR20180517005. Registered 17 May 2018.