Return to Play After Total Hip Arthroplasty: What Do Instrumented Hip Implants Teach Us? A Scoping Review

Background: Return to play (RTP) after total hip arthroplasty (THA) is increasingly expected by younger and more physically active patients. Current activity recommendations remain heterogeneous and are largely derived from expert opinion and indirect biomechanical modelling approaches, rather than direct in vivo biomechanical evidence. The aim of this article is to systematically map and synthesize the evidence from instrumented hip implant studies and to clarify how direct in vivo telemetry data can inform RTP counselling after THA. Methods: A scoping review was conducted according to a predefined Open Science Framework protocol and reported following PRISMA-ScR guidelines. MEDLINE (PubMed) and Scopus were searched from inception. Peer-reviewed clinical studies reporting direct in vivo biomechanical measurements obtained from instrumented hip implants were included. Conference proceedings, technical notes, reviews, and in vitro or computational-only studies were excluded. Data were extracted and synthesized descriptively according to activity domain, biomechanical variables, and implant technology. Results: Fifty studies met the inclusion criteria. Early investigations established feasibility and evolved from wired strain-gauge systems to fully implantable telemetric prostheses capable of measuring three-dimensional forces, moments, and friction-related parameters. Across cohorts, level walking consistently produced peak hip contact forces of approximately 2–3 times body weight, serving as a clinically meaningful reference loading envelope. Several recreational activities—including cycling, aquatic exercise, Nordic walking, and most gym-machine exercises—generally remained within or close to this range when performed with controlled technique. In contrast, certain rehabilitation tasks, forward-bent postures, lifting maneuvers, and perturbation events generated loads equal to or exceeding those observed during walking. Importantly, frictional moments and load direction showed substantial variability and may be more relevant to implant fixation than peak force magnitude alone. Conclusions: Instrumented hip implants provide objective biomechanical benchmarks that support principle-based and individualized RTP counselling, grounded in directly measured mechanical exposure rather than sport classification alone.