Background/Purpose: Knee osteoarthritis (KOA) often starts as a unilateral disease and commonly progresses to bilateral KOA. There is a need to identify mechanisms that explain unilateral to bilateral KOA progression. Loading is regarded as a risk factor for KOA. Thus, we aimed to explore relations between ground reaction force (GRF) symmetry metrics and cartilage worsening in the contralateral knee in persons with unilateral KOA. Although we explored posterior and medial-lateral GRF symmetry metrics, our primary hypothesis was that higher vertical GRF peaks, loading rates, and impulses in the contralateral limb relative to OA limb would be associated with cartilage worsening in the contralateral knee over 2 years.

Methods: We used data from the 144- and 168-month visits of the Multicenter Osteoarthritis (MOST) Study. Only those with unilateral radiographic KOA (i.e., Kellgren-Lawrence grade ≥2 in one knee) at the 144-month visit were included. At 144-months, three-dimensional GRFs were sampled at 1000 Hz during self-selected walking speed. From the GRF data, we determined peak vertical force and average vertical loading rate during the first half of stance, vertical impulse during stance (i.e., time integral), peak posterior force and posterior impulse during stance, peak medial and lateral forces during the first half of stance, and medial and lateral impulses during stance. All metrics were averaged across at least 3 trials and normalized to body weight. Symmetry angles (SAs) were calculated for each metric. An SA of 0 reflects perfect symmetry and positive values indicate greater GRFs in the contralateral limb. At both visits, MRIs were acquired and the knee without radiographic OA was read using the MRI Osteoarthritis Knee Score (MOAKS) system. Cartilage worsening in the knee without radiographic OA was defined as any increase, including within grade changes, in cartilage morphology score in the tibiofemoral joint from 144- to 168-months. Logistic regression was used to determine the relation of each GRF SA metric to cartilage worsening in the contralateral knee, adjusting for age, sex, and BMI. For each model, odd ratios and 95% confidence intervals were determined per one standard deviation increase in exposure.

Results: Our sample included 100 hundred MOST participants with unilateral KOA, with a mean(SD) age, BMI, and walking speed of 63.0(8.7) years, 29.4(5.2) kg/m², and 1.33(0.21) m/s, respectively; 60% female. Of these, 31% had tibiofemoral cartilage worsening in the contralateral knee over 2 years. GRF metrics are shown in Table 1. A one standard deviation increase in medial impulse SA was significantly associated with 42% decreased odds of cartilage worsening in the contralateral knee (Table 2). No other GRF symmetry metrics were associated with cartilage worsening.

Conclusion: In general, GRF symmetry metrics were not associated with cartilage worsening in the contralateral knee for those with unilateral KOA. Further research is needed to determine what meaningful differences in GRF metrics are and if the raw GRF metrics, rather than symmetry, relate to unilateral to bilateral KOA progression.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/three-dimensional-ground-reaction-force-symmetry-metrics-largely-fail-to-explain-cartilage-worsening-in-the-contralateral-knee-in-persons-with-unilateral-knee-osteoarthritis-the-multicenter-osteoarth/