Hip Abductor Muscle Strength in Patients After Total Knee Arthroplasty: A Systematic Review and Meta-analysis.

Introduction: Impaired hip abductor muscle strength indirectly leads to changes in knee kinematics and may cause pain or functional limitations after total knee arthroplasty (TKA). This study aimed to evaluate and quantify hip abductor muscle strength deficits after TKA and investigate external factors influencing hip abductor muscle strength after TKA.

Methods: A comprehensive literature search was performed, and clinical studies reporting hip abductor muscle strength after primary TKA were included. We performed meta-analyses to assess the relative hip muscle strength of the operated leg compared to the contralateral limb and the change from preoperative to postoperative values across multiple time points. We also assessed the pooled absolute hip muscle strength across the following time points: preoperatively, up to two months, two to six months, and more than six months postoperatively.

Results: There were 15 studies involving 823 patients that met our inclusion criteria. Compared with preoperative values, patients had a mean strength deficit of 18.0% (95% confidence interval (CI) [-30.8 to -5.2] at up to two months postoperatively, a non-significant deficit of 11.3% (CI [-32.7 to 10.2]) at two to six months postoperatively and an increase of 18.4% (CI [2.7 to 34.1]) at ≥ six months postoperatively. Compared with the contralateral side, patients had a mean abductor strength deficit of 11.5% (CI [-16.2 to -6.9]) preoperatively, 23.2% (CI [-27.6 to -18.8]) at up to two months postoperatively, a non-significant deficit of 10.8% (CI [-23.2 to 1.6]) at two to six months postoperatively and no difference (0.6% (CI [-4.2 to 5.4]) more than six months postoperatively. The study quality was low to moderate.

Conclusion: Hip abductor muscle strength is reduced preoperatively in patients undergoing TKA, continues to decrease in the immediate postoperative period, but fully recovers within six to 12 months. Although these data can be used to guide patient education and rehabilitation planning, they should be interpreted with caution due to the heterogeneous and limited high-quality evidence.