<p>Fully predictive simulations of sit-to-stand and stooping-down movements under various patient-specific conditions are created, with the goal of evaluating how these conditions influence the optimal placement of the acetabular cup following total hip arthroplasty. The assessment of hip-dislocation risk is based on implant impingement and edge-loading, which are widely recognized as significant contributors to this issue. The sit-to-stand and stooping-down motions are formulated as an optimal control problem, allowing for the prediction of movement patterns in response to different patient conditions, including knee pain, lumbar fusion, and variations in chair height. The predictive simulation results are compared with experimental measurements to validate the methodology. Findings reveal that knee pain induces more pronounced alterations in sit-to-stand movement patterns than lumbar fusion, resulting in increased hip-flexion angles and a reduced safety margin against impingement. Additionally, the results suggest that cup orientation determined from presurgery motion recordings may no longer be optimal postsurgery, as movement patterns shift when hip-joint pain is alleviated. These insights underscore the importance of patient-specific biomechanical factors in optimizing acetabular cup positioning to enhance postoperative stability.</p>