Low phase angle indicates poor muscle strength and physical performance in patients with knee osteoarthritis awaiting total knee arthroplasty.

Total knee arthroplasty (TKA) is commonly considered to improve physical function in patients with knee osteoarthritis (OA). However, factors related to pre- and postoperative physical performance remain unclear. Therefore, this prospective cohort study aimed to evaluate the association between the phase angle (PhA) determined via bioelectrical impedance and physical status in patients with knee OA awaiting TKA. In total, 226 patients (age 72.6 years; 35 males; 112 bilateral symptoms) were divided into low and high PhA groups; between-group differences and changes over time were analyzed. The low PhA group (n = 62) had significantly lower muscle strength and physical performance than did the high PhA group (n = 164). Of the cohort, 63 (27.9%) patients completed the 3-month postoperative assessment. While physical performance significantly improved in both groups, the low PhA group still exhibited poorer physical performance (P < .005). Multivariable analysis identified a low PhA as an independent risk factor for the 10-meter walk (β = -0.215; 95% confidence interval [CI]: -0.291 to -0.140) and log-transformed timed up-and-go test performance (β = 0.218; 95% CI 0.140 to 0.296) after adjusting for baseline covariates. A low PhA could indicate poor pre- and postoperative physical status in patients with knee OA.