OBJECTIVE: To examine if supervised progressive resistance training was superior to home-based exercise in rehabilitation after unicompartmental knee arthroplasty. DESIGN: Single blinded, randomized clinical trial. SETTING: Surgery, progressive resistance training and testing was carried out at Aarhus University Hospital and home-based exercise was carried out in the home of the patient. SUBJECTS: Fifty five patients were randomized to either progressive resistance training or home-based exercise. INTERVENTION: Patients were randomized to either progressive resistance training (home based exercise five days/week and progressive resistance training two days/week) or control group (home based exercise seven days/week). MAIN MEASURES: Preoperative assessment, 10-week (primary endpoint) and one-year follow-up were performed for leg extension power, spatiotemporal gait parameters and knee injury and osteoarthritis outcome score (KOOS). RESULTS: Forty patients (73%) completed 1-year follow-up. Patients in the progressive resistance training group participated in average 11 of 16 training sessions. Leg extension power increased from baseline to 10-week follow-up in progressive resistance training group (progressive resistance training: 0.28 W/kg, P= 0.01, control group: 0.01 W/kg, P=0.93) with no between-group difference. Walking speed and KOOS scores increased from baseline to 10-week follow-up in both groups with no between-group difference (six minutes walk test P=0.63, KOOS P>0.29). CONCLUSIONS: Progressive resistance training two days/week combined with home based exercise five days/week was not superior to home based exercise seven days/week in improving leg extension power of the operated leg.