G. Hatfield W. D. Stanish C. L. Hubley-Kozey;
Dalhousie Univ. Halifax NS CANADA.
Conservative interventions have been identified as the most important healthcare need for those with knee osteoarthritis (OA). While mechanical risk factors for knee OA progression have been identified via large epidemiological studies only one longitudinal study examined the knee joint local mechanical loading environment. They found that higher peak knee adduction moments (KAM) during walking were associated with increased risk of knee OA progression. While the most common gait variable reported in knee OA literature the peak KAM is a surrogate measure of medial compartment loading at one point in the gait cycle it neglects dynamic loading. Additionally three-dimensional (3D) gait variables are related to knee OA severity but their association to knee OA progression is not clear. This follow up study determined if there were differences in 3D knee biomechanical gait patterns between those with moderate knee OA who progressed to total knee arthroplasty (TKA) and those that did not.Methods:
50 patients with moderate medial compartment knee OA underwent gait analysis at baseline. Ground reaction forces (sampled at 1000 Hz) and segment motions (sampled at 100 Hz) were recorded during self-selected walking. Three-dimensional knee angles and moments were calculated using inverse dynamics. All waveforms were time-normalized to percent of gait cycle and moment waveforms were amplitude-normalized to body mass. Amplitude and temporal waveform characteristics were determined using Principal Component Analysis (PCA) for each waveform separately (6 in total). During follow up phone interviews 5-8 years later 25 patients reported undergoing TKA surgery. Unpaired Student’s t-tests were used to test for differences in all baseline demographic and waveform characteristics (PC scores) between the group that had TKA and the group that did not (α=0.05).Results:
There were no between-group differences in age (59 years in TKA group vs. 57 years in no-TKA group) mass (93.5 kg vs. 93.8 kg) body mass index (30.6 kg/m2 vs. 30.8 kg/m2) and gait speed (1.23 m/s vs. 1.27 m/s) with similar radiographic disease severity (Kellgren-Lawrence score) distribution at baseline. The mean time between baseline and follow up was 7.8 yrs for each group. The group that progressed to TKA had a significantly higher overall magnitude of the KAM (Fig 1 PC1 p < 0.05) less of a difference between the first peak KAM and the mid-stance KAM (Fig 1 PC2 p < 0.05) more tibial external rotation during mid-stance (PC4 p<0.05) and a trend toward reduced early stance knee flexion and late stance knee extension moments (PC2 p=0.073) than the no-TKA group at baseline.Conclusions:
The KAM findings suggest that the group that went on to TKA had higher overall medial compartment loading throughout the gait cycle at baseline (PC1) and a reduced ability to unload the medial compartment during mid-stance (PC2). These results support a cumulative rather than an impulse loading mechanism for progression. Furthermore increased tibial external rotation (PC4) and a trend toward altered sagittal plane moment characteristics (PC2) were found in those that progressed. Together these findings indicate that dynamic frontal transverse and sagittal plane mechanical features are related to knee OA progression and should be considered in future prediction models of progression.