Seventy-eight patients with knee osteoarthritis were randomized to receive knee extension exercise using the single-joint hybrid assistive limb (HAL-SJ; n=41) or conventional physical therapy (CPT; n=37) following total knee arthroplasty (TKA). The outcomes of interest were pain intensity during knee motion, active and passive knee extension angles, knee performance in terms of isometric knee extension strength (IKES), gait ability, standing and sitting abilities (assessed via the Timed Up and Go Test), and activities of daily living and quality of life (assessed via the Knee Injury and Osteoarthritis Outcome Scores, KOOS). Outcomes were assessed preoperatively and on postoperative days 1–10 and at weeks 2 and 4. Overall, the results of the study revealed that the HAL-SJ group experienced significant improvements in active and passive knee extension angles compared to the CPT group, with immediate improvements in active knee extension angle through day 5. However, there were no significant differences in pain, knee performance tests results and KOOS between the two groups.