Walking Distance and Interlimb Gait Differences Across 51 kg of Weight Loss After Total Knee Arthroplasty: A Three-Session Wearable Sensor Case Report
TL;DR
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, which cannot be attributed to weight loss specifically, because time since arthroplasty, rehabilitation exposure and repeated testing varied together with body mass.
Abstract
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.
