Ranking hip and knee joint contact forces during high-impact activities in high-functioning adults after hip or knee arthroplasty

BackgroundPeople with hip or knee joint arthroplasties are commonly advised to avoid high-impact physical activities, despite increasing demand to return to sport and vigorous exercise. Current implant testing standards do not reflect real-world loading during high-impact tasks, and few studies have quantified implant loads in high-functioning individuals who have returned to such activities. MethodsHigh-functioning adults with a total hip arthroplasty (THA, n = 11), total knee arthroplasty (TKA, n = 4), or unicompartmental knee arthroplasty (UKA, n = 3) performed a range of low-to high-impact activities, including walking, running, hopping, countermovement jumps, landings, and change-of-direction tasks. Three-dimensional trunk and lower-limb kinematics and ground reaction forces were collected. Musculoskeletal modelling was used to quantify three-dimensional hip and knee joint contact forces. Linear mixed-effects models were used to rank implant loads across activities and to compare peak resultant joint loads with healthy controls from a prior study. ResultsFor people with THR, relative to walking, a 45{degrees} change of direction generated the highest predicted hip contact force (8.38 BW, 95% CI 7.70-9.06), followed by running and unilateral hopping (all >1.5x walking, p < 0.05). Unilateral hopping and running produced the highest predicted knee contact force in TKA and UKA participants (8.0-9.1 BW), and both significantly greater than walking (p < 0.05). Compared with healthy controls, THA participants exhibited a lower predicted HCF during walking (-1.58 BW, 95% CI -2.46 to -0.69), but no group differences were observed for running, hopping, or jumping. ConclusionHigh-impact activities vary widely in model-estimated hip and knee contact forces. Several tasks were not substantially higher than walking. These data provide a biomechanical basis for evidence-informed activity prescription, regulatory implant testing, and future computational simulation of implant performance under realistic loading conditions.