Association between dynamic hip motion during gait and passive hip range of motion and muscle strength before and after total hip arthroplasty.

Background: While total hip arthroplasty (THA) for osteoarthritis (OA) provides pain relief and functional improvement, the postoperative recovery of gait patterns remains challenging. Residual abnormalities in hip biomechanics during gait may persist beyond one year postoperatively and are associated with joint overload, implant wear, and fall risk. Passive hip range of motion (ROM) and muscle strength are important determinants of joint mechanics, and should be examined in detail in relation to gait parameters. Understanding these relationships both before and in the early postoperative period is essential for developing individualized rehabilitation strategies. This study aimed to answer the following question: Do the maximum hip extension and adduction angles during the stance phase associate with the passive hip ROM and muscle strength before and after THA? In addition, we explored the potential contribution of muscle strength to these gait parameters, particularly in the early postoperative period.

Hypothesis: We hypothesized that reduced passive hip ROM would be associated with smaller maximum hip extension and adduction angles during the stance phase, both before and after THA.

Patients and methods: Twenty-five patients undergoing THA (mean age 66.5 ± 9.4 years, 72% female) were evaluated preoperatively and at discharge (23.6 ± 4.1 days postoperatively). Three-dimensional gait analysis was performed to assess maximum hip extension and adduction angles during the stance phase. Passive hip ROM was measured with a goniometer, and muscle strength was assessed using the hand-held dynamometer. Univariate and multivariate regression analyses were conducted to examine associations between gait parameters and ROM or muscle strength.

Results: Preoperatively, the hip extension and adduction angles during the stance phase were significantly associated with hip extension (r = 0.413, p = 0.040) and adduction (r = 0.575, p = 0.003) ROM, respectively, indicating that smaller joint angles were linked to reduced ROM. Conversely, in the early postoperative period, the hip extension angle was significantly associated with extension ROM (r = 0.480, p = 0.015) and extensor strength (r = 0.484, p = 0.014), such that smaller angles were observed in patients with reduced ROM and lower strength. However, the adduction angle was not associated with hip ROM and muscle strength.

Discussion: This study suggests that rehabilitation should focus on hip extension ROM and extensor strength to improve gait patterns during the early postoperative period after THA. These results provide useful insights for the development of individualized postoperative rehabilitation plans.

Level of evidence: III; single-center, retrospective observational study.