Abstract / Summary
Background and Clinical Significance: Longitudinal observations that combine major postoperative weight loss with limb-specific gait assessment after total knee arthroplasty (TKA) are uncommon. This case report describes three single-trial instrumented assessments in one patient and is intended as a descriptive observation; it does not establish causality, measurement stability, mechanical loading, or a clinically meaningful persistent deficit; Case Presentation: A man in his early sixties at the first assessment had undergone left TKA for end-stage osteoarthritis and subsequently underwent Roux-en-Y gastric bypass. Three assessments were available from approximately 31 to 67 months after TKA. Body mass was 120, 88, and 69 kg (body mass index 43.03, 31.55, and 24.74 kg/m2), while two-minute walk distance (2MWT) was 67.8, 105.1, and 118.1 m. The third walk test was launched in the software’s six-minute module and stopped at 1 min 58 s, so 118.1 m is the distance accumulated over 118 s and was neither adjusted nor extrapolated to 120 s. The operated limb showed longer stance duration than the non-operated limb by 3.04, 5.28, and 2.05 percentage points, and a proprietary propulsion index was lower on the operated side by 18.18%, 17.95%, and 14.06%; the direction of both differences was the same at every session but the magnitude was not, and the index has no published calculation or post-TKA interpretive threshold. Each session comprised one trial, and the third-session gait means were based on only five operated-limb and four non-operated-limb steps. Valid Timed Up and Go (TUG) totals were available for sessions 1 and 2 (13.41 and 14.95 s); the available source documentation did not contain a valid session-3 TUG result. Vendor-derived walk-test speed was excluded from primary interpretation because its calculation could not be reconciled with distance divided by test duration; Conclusions: Across these three observations, 2MWT distance increased while side-to-side differences in stance duration and the exploratory propulsion index were present at each session. These co-occurring changes cannot be attributed to weight loss specifically, because time since arthroplasty, rehabilitation exposure and repeated testing varied together with body mass. The findings are descriptive and hypothesis-generating; confirmation requires prospective studies with repeated trials per session, an adequate number of analysed steps, and validated kinetic or limb-specific outcomes.