Pelvic and lower limb compensatory actions of subjects in an early stage of hip osteoarthritis

Objective: To determine if compensatory actions take place at the pelvis an d other joints of the affected lower limb in subjects who were in an early stage of hip osteoarthritis (OA). Design: Nonrandomized, case-control study. Setting: A gait laboratory. Participants: Seventeen patients with OA of the hip (clinical group) matche d with 17 healthy elderly subjects (nonclinical group). Interventions: Video data obtained while subjects walked a 10-meter walkway twice and stepped across a forceplate. Main Outcome Measures: Four phasic and temporal gait parameters (walking sp eed, stance phase relative duration, stride length, cadence) 10 pelvic (pel vic tilt, obliquity, rotation at push-off maximum range of motion for all 3 ) and hip (3 hip angles at push-off, maximum hip flexion) kinematic paramet ers, 3 hip moments, and twenty-seven 3-dimensional peak muscle powers (labe led by joint, peak power, plane) developed in the lower limb joints during the gait cycle. Results: Subjects in the clinical group were characterized by a 12.4% slowe r walking speed. The pelvis was more upwardly tilted (2.5 times) at push-of f in the clinical group than in the nonclinical group. Obliquity, measured in the frontal plane, revealed that the pelvis dropped more (2.4 times) on the unsupported limb of the clinical group at push-off. In the sagittal pla ne, subjects in the clinical group absorbed less energy in their second hip peak power for decelerating the thigh extension and generated less hip pul l (third hip peak power) than the nonclinical group by 34% and 29%, respect ively. In the sagittal plane, the clinical group had 57% lower second knee peak power to straighten the joint shortly after heel strike, and 43% less knee absorption (third peak power) at push-off. During the push-off phase, the clinical group developed more than twice their third peak knee power in the frontal plane and 5 times more their third peak knee power in the tran sversal plane than the peak knee power of the nonclinical group in an attem pt to control knee adduction and to facilitate body-weight transfer by an i nternal rotation. At the end of the swing phase, the fourth peak power in t he sagittal plane showed the absorption power required to decelerate the le g; it was reduced by 35% in the clinical group, representing a strategy to increase walking speed by lengthening the stride length. Conclusions: Even at an early stage of hip OA, joint degeneration was compe nsated by an increase in pelvis motion and muscle power generation or absor ption modifications in other lower limb joints.