Background: Total hip arthroplasty is considered an efficacious procedure for relieving pain and disability, but despite that objectively measured physical activity level remains unchanged compared to pre-surgery and is still considerably lower than that of a healthy age- and sex-matched population 6-12 months post-surgery. Since there is a graded relationship between physical activity level and functional performance, increasing physical activity may enhance the outcome of the procedure. This study aims to investigate whether promotion and support of physical activity initiated 3 months after total hip arthroplasty complementary to usual rehabilitation care can increase objective measured physical activity 6 months post-surgery.

Methods: The trial is designed as a pragmatic, parallel group, two-arm, assessor-blinded, superiority, randomized (1:1), controlled trial with post intervention follow-up 6 and 12 months after total hip arthroplasty. Home-dwelling, independent, and self-reliant patients with hip osteoarthritis are provisionally enrolled prior to surgery and rescreened about 2-3 months post-surgery to confirm eligibility. Baseline assessment is conducted 3 months post-surgery. Subsequently, patients (n=200) are randomized to either a 3-month, multimodal physical activity promotion/education intervention or control (no further attention). The intervention consists of face-to-face and telephone counselling, patient education material, pedometer, and step-counting journal. The primary outcome is objectively measured physical activity, specifically the proportion of patients that complete on average >= 8000 steps per day 6 months post-surgery. Secondary outcomes include core outcomes (i.e., physical function, pain, and patient global assessment) and health-related quality of life. Furthermore, we will explore the effect of the intervention on self-efficacy and outcome expectations (i.e., tertiary outcomes).

Discussion: By investigating the effectiveness of a pedometer-driven, face-to-face, and telephone-assisted counselling, behavior change intervention in complementary to usual rehabilitation, we hope to deliver applicable and generalizable knowledge to support physical activity after total hip arthroplasty and potentially enhance the outcome of the procedure.