Leg loading during quiet standing and sit-to-stand movement for one year after total hip arthroplasty

Background: The objective of the present study was to investigate loading of the operated leg during quiet standing and sit-to-stand (STS) movement for 1year after total hip arthroplasty (THA). Methods: One hundred and fifty-eight patients with end-stage hip osteoarthritis (OA) who had undergone unilateral primary THA participated in this study. The load distribution on the operated and non-operated legs was computed by measuring the vertical reaction force of the operated and non-operated legs during quiet standing and STS movement. We investigated the load distribution using Pressure Distribution Measurement Platform preoperatively and 1, 2, 3, 6, and 12months postoperatively. Findings: Loading of the operated leg during quiet standing was restored 1month postoperatively. Loading of the operated leg during STS movement was higher within 2months postoperatively than the preoperative levels and continued to increase 1year postoperatively. Loading of the operated leg was lower during STS movement than that during quiet standing, even 1year postoperatively. Interpretation: A longitudinal and dynamic assessment of loading of the operated leg after THA is clinically important, and the loading during STS movement might continue to increase for a year after THA.