Rate of Force Development in the Quadriceps of Individuals With Severe Knee Osteoarthritis: A Cross-Sectional Study

We tested the following hypotheses: individuals with severe knee osteoarthritis (KOA) would display a significantly decreased quadriceps rate of force development (RFD); and this decrease would be greater than the decrease in maximum quadriceps strength. Maximum isometric strength of the quadriceps was assessed in individuals with mild (Kellgren and Lawrence [K&L] grade 1–2) and severe KOA (K&L grade 3–4). RFD was analyzed at 200 ms from torque onset and normalized to body mass and maximum voluntary isometric contraction torque. The decrease in quadriceps RFD and the difference between this and the decrease in maximum quadriceps strength was tested with logistic regression analysis with a propensity-score-adjusted model and analysis of covariance, respectively. Effect size by Hedges’ g with a 95% confidence interval (CI) was calculated for the quadriceps RFD and maximum quadriceps strength. Sixty-six participants were analyzed. Individuals with severe KOA displayed significantly decreased quadriceps RFD (odds ratio: 0.50; 95% CI: 0.26-0.82), the decrease being greater than that in maximum quadriceps strength (between-group difference, ES: 0.88, -1.07 vs. 0.06, -0.22). The results suggest that a decreased quadriceps RFD is a modifiable risk factor for progressive KOA. This could lead to the early detection and prevention of severe KOA.