Abstract
Introduction
Patients with knee osteoarthritis (OA) often tell us that they put extra load on the joints of the opposite leg as they walk. Multiple joint OA is common and has previously been related to gait changes due to hip OA (Shakoor et al 2002). The aim of this study was to determine whether patients with medial compartment knee OA have abnormal biomechanics of the unaffected knee and both hips during normal level gait.
Methods
Twenty patients (11 male, 9 female), with severe medial compartment knee OA and no other joint pain were recruited. The control group comprised 20 adults without musculoskeletal pain. Patients were reviewed, x-rays were examined and WOMAC and Oxford knee scores were completed. A 12 camera Vicon (Vicon, Oxford) system was used to collect kinematic data (100Hz) on level walking and the ground reaction force was recorded using three AMTI force plates (1000Hz). Surface electrodes were placed over medial and lateral quadriceps and hamstrings bilaterally to record EMG data (1000Hz). Kinematics and kinetics were calculated using the Vicon ‘plug-in-gait’ model. A co-contraction index was calculated for the EMG signals on each side of the knee, representing the magnitude of the combined readings relative to their maximum contraction during the gait cycle. Statistical comparisons were performed using t-tests with Bonferroni's correction for two variables and ANOVA for more than two variables (SPSS v16).
Results
The mean age of the patients was 69 (SD 8.8). Mean gait speed was 0.95m/s (study group) and 1.44m/s (control group). Peak adduction moments for the OA group [OA Knee; Unaffected Knee; Ipsilateral Hip; Contralateral Hip; in Nm/Kg(±95% CI)] were: 0.55(0.06); 0.47(0.06); 0.73(0.09); 0.73(0.08). Control values for peak moments were 0.64 (0.06) for the knee and 0.81(0.07) at the hip. Mid-stance adduction moments for the OA group (listed as before) were: 0.44(0.08); 0.33(0.06); 0.64(0.06); 0.61(0.08). Control values for mid-stance moments were 0.14(0.03) and 0.40(0.04). [OA group vs. Controls: p=NS for peak moments at all 4 joints; p<0.01 for mid-stance moments at all joints]. Co-contraction indices for hamstrings and quads, [OA knee medial; and lateral; unaffected knee medial; and lateral; control medial; and lateral; 0<X
Discussion
Although the affected subjects all had only single joint OA, abnormal moments were present in the hips and knees of both legs during normal level gait, despite the reduced gait speed of the OA cohort. Abnormal hamstring and quadriceps co-contraction occurs bilaterally in patient with single joint OA.
Increased trunk sway is a recognised compensation in knee OA and may be the cause of the abnormal hip and contra-lateral knee loading found in this study. Further investigation is warranted and may lead to improvements in the long term outcome for these patients.
Acknowledgement
The study was funded by the North Wales NHS Trust.
