Temporal changes in quadriceps and hamstring strength and flexibility following total knee arthroplasty

Purpose: Quadriceps and hamstring dysfunction is well-documented in individuals with knee osteoarthritis (OA) and after total knee arthroplasty (TKA). While strength deficits are often studied, changes in muscle flexibility and their influence on postoperative recovery remain less understood. Objective: This study aimed to evaluate temporal changes in quadriceps and hamstring strength and flexibility from the preoperative stage to one year following TKA and to compare with those of healthy controls. Methods: Individuals with knee OA scheduled for TKA were assessed for quadriceps and hamstring strength using a handheld dynamometer and for flexibility using standardized muscle length tests. Measurements were obtained preoperatively and at 6 weeks, 3 months, 6 months, and 12 months postoperatively, and were compared with age- and sex-matched healthy controls. Statistical significance was set at p < 0.05. Results: Preoperatively, quadriceps and hamstring strength were significantly reduced compared with controls (p < 0.001). Strength declined further at 6 weeks post-TKA, particularly in the quadriceps. Significant improvements were observed from 3 to 12 months postoperatively (p < 0.001). At 12 months, quadriceps and hamstring strength remained significantly lower than controls (p < 0.001). Quadriceps and hamstring flexibility was significantly reduced postoperatively (p < 0.05) and demonstrated gradual improvement over time, corresponding with strength recovery. Conclusion: Quadriceps and hamstring strength and flexibility improved substantially during the first postoperative year following TKA; however, residual quadriceps deficits persisted relative to healthy controls. These findings highlight the need for early and progressive rehabilitation strategies emphasizing long-term quadriceps strengthening and flexibility training to optimize postoperative outcomes.