Abstract
Summary Statement
This study provides preliminary evidence that people with knee osteoarthritis have greater asymmetry in joint loading than healthy controls. Altered loading of the contralateral limb may signify increased risk of injury to other lower limb joints in knee osteoarthritis.
Introduction
Compensatory overloading of other lower limb joints is a potential reason for the non-random evolution of osteoarthritis (OA). In individuals with knee OA altered joint loading exists of the contralateral cognate joints. However, previous studies have neglected the temporal features of asymmetry in joint loading. The study aimed to identify the amount and temporal features of asymmetry in lower limb joint loading in advanced knee OA.
Patients and Methods
Participants (n=15) were awaiting primary unilateral total knee replacement for OA (age 67.0 SD 8.9 years, height 1.66 SD 0.13 m, mass 84.2 SD 15.8 kg, BMI 30.7 SD 6.2 kg/m2, median KL grade 4). Data were compared to asymptomatic age and sex matched controls. Kinematic and kinetic data during walking was acquired with 12 cameras (VICON MX-F20) and two Kistler force platforms at 100 Hz and 400 Hz respectively. Data were analysed in Visual3D (C-Motion Inc., USA). Asymmetry was computed in MatLab using a recently published symmetry index (SI) and symmetry function (SF). Variables (computed using inverse dynamics) were the peak external moments (%BW∗Height) of the hip, knee and ankle. Differences between means of the SI variables in the OA and control groups were compared using Student's t-tests. Discrete variables were also compared between limbs (paired t-test) or between the affected limb and matched control limb. Effect sizes (Cohen's d) for the differences were also computed.
Results
A significant between group difference (OA and control) for SI was observed for the transverse plane ankle joint moment (16.1 SD 8.0 vs. 10.4 SD 4.8 d = 0.8 p = 0.049). A large effect size for the sagittal plane knee joint moment (22.9 SD 12.1 vs. 12.7 SD 5.1 d = 1.1 p = 0.178) and a medium effect size for the transverse plane hip joint moment (26.4 SD 15.9 vs. 16.6 SD 9.0 d = 0.7 p = 0.098) were observed. The unaffected limb (OA group) had higher peak hip flexion (5.76 SD 1.49 vs.5.32 SD 1.51 p = 0.041) and internal rotation moments (−0.67 SD 0.34 vs. −0.41 SD 0.18 d = 0.004) and a lower ankle inversion moment (0.16 SD 0.14 vs. 0.34 SD 0.24 d = 0.9 p = 0.030) compared to the affected limb. Only the difference in the first peak knee adduction moment for the affected and matched control limb was statistically significant (−2.65 SD 1.38 vs. −2.16 SD 1.16 d = 0.7 p = 0.031).
Discussion and Conclusion
This study provides preliminary evidence of more asymmetry in joint moments of the lower limb in people with knee OA compared to controls. Further investigation with a larger sample is required to verify these findings. Altered loading of the contralateral cognate joints may signify increased risk of injury at the hip and ankle and highlights the need for monitoring of other lower limb joints in knee OA.
