Kinematic variability and local dynamic stability of gait in individuals with hip pain and a history of developmental dysplasia.

BACKGROUND: Individuals with developmental dysplasia of the hip (DDH) often report hip pain and exhibit gait adaptations. Previous studies in this patient population have focused on average kinematic and acceleration measures during gait, but have not examined variability.

RESEARCH QUESTION: Do individuals with hip pain and DDH have altered kinematic variability or local dynamic stability (LDS) compared to individuals without hip pain?

METHODS: Twelve individuals with hip pain and DDH and 12 matched controls walked for two minutes on a treadmill at three speeds: preferred, fast (25% faster than preferred), and prescribed (1.25 m/s). Kinematic variability of spatiotemporal measures, joint and segment angles, and LDS of the trunk were calculated for each speed.

RESULTS: At the prescribed speed, individuals with hip pain and DDH had more kinematic variability than controls at the hip, pelvis, and trunk as well as greater variability in spatiotemporal measures. LDS was not different between groups. Kinematic variability of the joints decreased and LDS of the trunk increased (i.e., increased gait stability) with increased speed.

SIGNIFICANCE: Individuals with hip pain and DDH had greater kinematic variability compared to individuals without hip pain when walking at the same prescribed speed, indicating either an adaptation to pain or reduced neuromuscular control. LDS of the trunk was not different between groups, suggesting that hip pain does not affect overall gait stability. Kinematic variability and LDS were affected by walking speed, but in different ways, emphasizing that these measures quantify different aspects of walking behavior.