Dynamic joint stiffness and co-contraction in subjects after total knee arthroplasty
Date
2011
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Publisher
University of Delaware
Abstract
Background: Altered gait patterns and movement strategies that exist before total knee arthroplasty (TKA) can persist after surgery and can be detrimental to the prosthesis and the other joints in the leg. The purpose of this study was to examine dynamic joint stiffness and co-contraction in the lower limbs joints after total unilateral knee arthroplasty. Methods: A cross-sectional design was used with 36 subjects at 6 months after TKA, 48 subjects at 1 year after TKA, and 22 healthy controls. Joint excursions, peak joint moments, and co-contraction across the joints were measured. Dynamic joint stiffness was calculated as the moment divided by the angle during gait. Kinematic and kinetic data were collected using 2 in-ground force plates and an 8-camera motion capture system. EMG data was collected using 16 surface electrodes on the lower limb muscles. Repeated measures ANOVAs were used to compare differences between groups (6 month, 1 year, and control) and between limbs (operated and non-operated). Correlations between joint stiffness and co-contraction were also calculated. Findings: Stiffness was higher in the operated knee in the 6 month group as well as in the operated limb (p=0.002, p=0.016). There was also a significant group by limb interaction effect (p=0.022). No significant differences were found in co-contraction between groups at the knee. Ankle stiffness was lower in the 1 year group (p=0.001).