Preoperative lower limb skeletal muscle mass impact functional rehabilitation and mobility ability after total knee arthroplasty for osteoarthritis: a prospective, observational study

Background: Despite the remarkably successful treatment of total knee arthroplasty (TKA), several patients also dissatisfied with their function, not met preoperative expectations. The purpose of this study was to investigate the relationship between preoperative lower limb skeletal muscle mass (LSM) and early functional rehabilitation outcome after TKA. Methods 102 patients who underwent a primary unilateral TKA were enrolled to our prospectively observational study. Preoperative variables included demographic (socio-demographic data and disease-related information), LSM, lower limb muscle strength. The HSS and WOMAC-Function scales was used to evaluate knee functional rehabilitation outcome and mobility ability at the time points of preoperative, 3 months and 6 months after TKA. Univariate and multivariate regression analysis was performed with the evaluations at 6 months after TKA as the main outcome measures. Results Multivariate Logistic regression analysis showed that LSM (β = 4.367, p = 0.000) was positively related to functional rehabilitation measured by HSS at 6 months postoperatively; age (β=-0.104, p = 0.007), postoperative pain (β=-1.311, p = 0.000) were negatively related to HSS. The preoperative lower limb skeletal muscle mass showed a significant negative relationship with the postoperative functional activity ability assessed by WOMAC-Function scale (β=-0.208, P  = 0.006). Conclusion Lower limb skeletal muscle mass positively impacted on functional rehabilitation and knee mobility ability after TKA in patients with osteoarthritis. LSM should be considered when considering patient`s expectation to achieve higher demanding tasks.