Knee Joint Biomechanics in People with Medial Compartment Knee Osteoarthritis
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Background: Sagittal plane external flexion moment in early stance has been reported to be both higher and lower in people with medial knee OA compared to control subjects. Purpose: Sagittal plane knee joint kinetics and kinematics were compared between people with medial compartment OA and healthy subjects. Subjects with OA and low pain scores were also compared to those with OA and moderate pain scores. Subjects: Forty people with medial knee OA and 40 age and sex matched control subjects. Method: Knee alignment and OA severity were measured from radiographs. Frontal and sagittal plane moments and knee flexion angle during gait were measured using a three dimensional motion analysis system and force plates. The Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) was used to measure pain; this score was used to divide the OA group into low pain and moderate pain OA groups. The relationship between knee flexion moment in early stance and gait speed, knee flexion angle and pain was also determined. Results: Subjects with OA had lower gait speed and cadence, and higher double limb support time. Peak knee adduction moment (first 50% of the gait cycle) was higher in the OA group. The knee flexion moment in early stance did not differ between groups; however the knee extension moment in late stance was lower in the knee OA group. The moderate pain group walked more slowly than the low pain group. The knee adduction moment, sagittal plane moments and knee flexion angle in stance did not differ between OA groups. A positive correlation was found between knee flexion moment and knee flexion angle in early stance in the knee OA group; the correlations between knee flexion moment and pain and gait speed were not significant. Conclusion: No differences were found in the knee flexion moment or stance phase knee flexion angle between the groups compared in this study, and therefore the results do not contribute to resolution of the controversy in the literature. Participants with knee OA in this study had relatively mild to moderate disease severity, which may have contributed to the non-significant findings.