Lower limb inter-joint coordination in individuals with osteoarthritis before and after a total knee arthroplasty.

Background: Total knee arthroplasty is the most common treatment for severe knee osteoarthritis. Coordination and variability analyses are effective measures of the injury stage or rehabilitation process. This study compared the inter-joint coordination before and after arthroplasty, compared to controls.

Methods: Twenty-seven patients were evaluated before and 12 months after surgery, compared to 27 controls. Coordination and variability in the sagittal plane between the hip-knee and knee-ankle were calculated using vector coding and circular statistics. Coordination was categorized as in-phase, anti-phase, or distal or proximal joint-phase. The gait cycle was divided into sub-phases for the coordination, variability, and range of motion results.

Findings: Coordination and range of motion differed significantly between the patient groups and controls, while small differences between pre- and post-operative groups were also detected. The hip-knee showed a reduced in-phase frequency in the patient group compared to control during stance, particularly mid-stance: pre-operative 24.3% ± 33.9, post-operative 29.5 ± 29.7, and controls 70.7 ± 17.0. This difference was compensated for by increasing proximal-phase (hip) frequency in the patient groups. For knee-ankle coordination, the patient groups showed higher distal-phase (ankle) frequency during the early and mid-stance. Coordination variability was higher post-operatively during swing and terminal swing phases, compared to controls.

Interpretation: The results indicated reduced degrees of freedom for the knee during stance phase with a reduced capacity to move the knee and hip in opposing directions before and one year after surgery. The patient group after the surgery increased knee range of motion and coordination compared to pre-operative during swing phase.