Mobility Outcomes Testing Following Total Knee Arthroplasty: Improving on Subjective Outcomes Reporting: A Pilot...

Patient-reported outcome measures (PROMs) are widely used to assess recovery following total knee arthroplasty (TKA) but are limited by subjectivity and recall bias. This initial pilot study introduces a novel Mobility Outcomes Testing Battery (MOTB) designed to objectively evaluate functional recovery using real-time movement and pain assessments.

Thirty-six patients undergoing primary TKA completed MOTB and PROMs (Knee injury and Osteoarthritis Outcome Score Jr, Pain Catastrophizing Scale, TSK-11) preoperatively and at 3 and 6 months postoperatively. MOTB included eight functional tasks (walking, sit-to-stand, stair ambulation) scored on performance (0 to 2 scale) and real-time pain (VAS 0 to 10). Composite MOTB scores were calculated by combining function and pain metrics. Dual-energy radiograph absorptiometry was used to assess body composition and skeletal dimensions. Radiographic limb alignment and demographic data were also collected. An analysis of variance was used to detect changes in measures over time, Pearson correlations examined the relationship between MOTB and standard PROM scores, and stepwise linear regression identified predictors of 6-month MOTB performance.

MOTB scores improved markedly from baseline to 3 months (0.001) and from 3 to 6 months ( P = 0.008), demonstrating greater sensitivity than PROMs for detecting functional change. MOTB correlated with Knee injury and Osteoarthritis Outcome Score Jr. (r = 0.715, P < 0.001), Pain Catastrophizing Scale (r = -0.445), and TSK-11 (r = -0.359). Movement-specific analysis revealed stair descent as the most challenging task, with only 50% of patients achieving optimal scores at 6 months. Regression analysis identified higher preoperative lean mass and leg length as predictors of better stair performance, whereas increased body fat, valgus alignment, and cardiovascular disease were associated with poorer outcomes. Limb alignment classification (varus vs. valgus) had the strongest influence on cumulative MOTB scores.

The MOTB offers a practical, objective, and movement-specific alternative to PROMs, with greater sensitivity to functional changes and reduced subjectivity. Easily implemented in minutes with no large equipment required, its potential in-clinic utility may enable individualized rehabilitation tracking and guide recovery by identifying movement deficits and modifiable risk factors.