The purpose of this study was to identify biomechanical variables indicative of lower extremity dysfunction, distinct from age-related gait adaptations, and to examine interrelationships among these variables to better understand the mechanisms underlying neuromuscular adaptations in gait. Sagittal plane ankle, knee and hip peak angles, moments and powers, and spatio-temporal parameters, were acquired during preferred speed gait in 120 subjects: 45 healthy young, 37 healthy elders, and 38 disabled elders with functional limitations due to lower-extremity musculoskeletal pathology--primarily arthritis. MANCOVA with discriminate analysis, statistically controlled for gait speed, was used to identify the important variables distinguishing between groups. Correlation analysis was then used to explore interrelationships among these variables within each group. Healthy elderly subjects were discriminated (sensitivity 76%, specificity 82%) from young subjects via decreased late-stance ankle plantar flexion angle, and increased late-stance knee power absorption and early-stance hip extensor power generation. Disabled elderly subjects were discriminated (sensitivity 74%, specificity 73%) from healthy elderly subjects via decreased late-stance ankle plantar-flexor moment and ankle plantar-flexor power generation, and increased early-stance ankle dorsi-flexor moment, late-stance hip flexor moment, and late-stance hip flexor power absorption. Relationships among these variables showed a higher degree of coupling for the disabled elderly subjects compared to the young and elderly healthy subjects, suggesting a reduced ability to alter motor strategies. Our data suggest that, beyond age-related changes, the elders with lower-extremity dysfunction rely excessively on passive action of the hip flexors to provide propulsion in late-stance, and ankle dorsi-flexors of the contralateral limb to provide trunk stability. These findings support a growing body of evidence that changes in gait with age and disablement has a neuromuscular basis, which may be informative in a motor control framework for physical therapy interventions.