Preserving Mobility Across the Healthspan: How Knee Injury Reshapes Gait Bioenergetics, Mobility, and Lean Soft Tissue Quality

Abstract

This dissertation investigated how knee injury shapes mechanical efficiency, joint mechanics, intersegmental coordination, and lower-limb muscle composition in adults across the healthspan. The first aim was to determine whether adults with a history of knee injury exhibit reduced mechanical efficiency during walking compared to non-injured controls, and whether intersegmental coordination contributes to this difference. Forty-one community-dwelling adults completed user-driven treadmill walking with simultaneous indirect calorimetry and three-dimensional motion capture. Adults with a history of knee injury demonstrated approximately 5.5% lower efficiency of positive work than those without a history of knee injury, with the magnitude of this deficit varying with walking speed. Joint power symmetry across the hip, knee, and ankle was preserved between groups, indicating that kinetic symmetry coexisted with energetic deficits. Intersegmental coordination at the previously injured knee was associated with mechanical efficiency in ways that differed between groups; this relationship was absent at five other lower-limb couplings. The second aim examined whether adults with a history of knee injury exhibit greater interlimb fat-to-muscle ratio (FMR) asymmetry in the quadriceps, hamstrings, and calf, and whether this asymmetry is associated with functional mobility. Lateral dual-energy X-ray absorptiometry and inertial measurement units quantified compositional asymmetry and performance on Osteoarthritis Research Society International–recommended assessments. Adults with a history of knee injury exhibited approximately two-fold greater interlimb FMR asymmetry across all three compartments despite minimal between-group differences in bilateral pooled composition. Quadriceps FMR asymmetry was associated with poorer transitional-task performance but not walking speed, and overall thigh FMR asymmetry was associated with a temporal gait rhythm component. These studies have important implications for understanding how knee injury reshapes mobility across the healthspan and provide empirical engagement with the Integrated Knee Health-Mobility Model framework introduced in Chapter 2. They elucidate the next steps in developing multimodal assessment strategies and targeted rehabilitation approaches for adults with a history of knee injury to preserve mobility across the healthspan.