Effects of Supplemental Robot-Assisted Knee Flexion Exercise After Total Knee Arthroplasty: A Randomized Controlled Clinical Study

Abstract

OBJECTIVES: This study aimed to investigate the beneficial effects of single-joint hybrid assistive limb (HAL-SJ)-assisted rehabilitation after total knee arthroplasty (TKA), with a focus on the early postoperative period. METHODS: This single-anonymized randomized controlled trial assigned 72 participants who underwent primary TKA for knee osteoarthritis to the HAL-SJ (n=35) and control groups (n=37). The passive knee range of motion (ROM; i.e., the primary outcome) was evaluated preoperatively and at 1 week, 2 weeks, and 3 months postoperatively. Extension lag and knee pain intensity scores were evaluated preoperatively and at 1 and 2 weeks postoperatively. Quadriceps and hamstring isometric knee strength and walking speed were evaluated preoperatively and at 2 weeks postoperatively. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was evaluated preoperatively and at 3 months postoperatively. RESULTS: Compared with the control group, the HAL-SJ group showed significantly improved knee extension ROM (p=0.001) and greater KOOS Activities of Daily Living subscale score (p=0.005) at 3 months postoperatively, with a significantly early improvement in extension lag (p=0.001) and hamstring strength (p=0.012) at 2 weeks postoperatively. CONCLUSIONS: HAL-SJ effectively supports postoperative rehabilitation, showing clinical advantages for improving daily activities by 3 months after TKA. CLINICAL TRIAL REGISTRATION: University Hospital Medical Information Network (UMIN000053675).