Component rotational mismatch in the standing position is a potential risk factor for unfavourable functional outcomes after total knee arthroplasty

Purpose This study assessed rotational mismatch between components after total knee arthroplasty (TKA) in the supine and standing positions and aimed to investigate the effect of rotational mismatch in the standing position on postoperative patient‐reported outcome measures (PROMs). Methods Seventy‐one patients (71 knees) who underwent TKA for medial knee osteoarthritis were used to investigate rotational mismatches between components. Rotational mismatches between components were examined on postoperative standing whole‐leg and supine knee radiographs using a three‐dimensional‐to‐two‐dimensional model image registration technique, and the angles between the reference axes of the components were measured. Component alignment was evaluated using postoperative computed tomography images, and a questionnaire (2011 version of the Knee Society Score: [KSS 2011]) was mailed to investigate postoperative PROMs. Results In the entire cohort, rotational mismatches in the supine and standing positions were similar (p = 0.9315). In 15% of patients, the mismatch was large (>5°) in the supine position but small (