Purpose <p>(1) to establish an objective measure of postoperative physical performance following hip arthroscopy using a markerless motion-capture system to analyze the Landing Error Scoring System (LESS) and (2) to validate the postoperative LESS test by evaluating its correlation with postoperative PROs.</p> Methods <p>Data were prospectively collected and retrospectively analyzed for patients who underwent hip arthroscopy from October 2017 to December 2019. Inclusion criteria were patients having undergone hip arthroscopy with minimum 1-year follow-up, pre- and postoperative PROs, and postoperative LESS. Protocol was for LESS to be performed 6 months postoperatively. Participants successfully completed three trials of a jump-landing movement assessment. The LESS data and 3-dimensional motion analysis were collected simultaneously during the jump-landing task. The LESS score is a summation of landing technique “errors,” using a range of readily observable aspects of human movement. This LESS score was examined for possible correlation with postoperative PROs.</p> Results <p>3-month and 1-year postoperative mHHS, NAHS, VAS, and VR-P were significantly correlated with postoperative LESS scores. 3-month postoperative iHOT and 1-year postoperative SF-P were significantly correlated with postoperative LESS. No significant correlation was found between LESS scores and 3-month or 1-year postoperative HOS-SSS, 1-year postoperative iHOT or 3-month postoperative SF-P. No correlation was found between SF-M or VR-M and postoperative LESS scores at any study time points.</p> Conclusion <p>LESS, analyzed by a markerless motion capture system, may correlate with 3-month and 1-year PROs following hip arthroscopy. Pure mental questionnaires do not show significant correlation between the two assessment tools. This study suggests validation of LESS as an objective measure of postoperative physical performance.</p>