Quadriceps rate of force development following total knee replacement is associated with gait speed – low-cost clinically feasible methodology

Background: Rate of force development (RFD) is a measure of how rapidly a muscle can produce force. Insufficient quadriceps strength and RFD following total knee replacement (TKR) may be associated with reduced physical function, physical activity and gait speed. We recently developed a valid and reliable RFD testing protocol using a hand-held dynamometer (HHD) and freely-available software [1]. However, the clinical relevance of this protocol is yet to be assessed in people following TKR. Hypothesis: Greater quadriceps strength/RFD would be associated with better knee function, higher physical activity levels and greater gait speed.Methods: Fifty-five people (26 women, mean age 69±8, mean 4±1 months post TKR) volunteered to participate. Quadriceps peak torque and RFD were assessed in 90 degrees knee flexion using a Lafayette HHD. RFD was calculated using custom software. Knee pain (VAS), knee function (Oxford scale), physical activity (International Physical Activity Questionnaire) and gait speed (6-metre walk test) were assessed concurrently. Pearson r values were used to determine associations between variables.Results: The operated limb had significantly lower body-weight-normalized quadriceps strength (p<0.001, 31% difference) and RFD (p<0.001, 32% difference) than the contralateral side. There were no significant associations between quadriceps strength/RFD and knee pain, knee function or physical activity. There were significant moderate correlations between gait speed and quadriceps RFD on the operated (r=0.45) and contralateral side (r=0.57) and quadriceps strength on the contralateral side (r=0.46).Conclusion: Quadriceps RFD on either limb may be an important determinant of gait speed following TKR. 1.Mentiplay BF, Perraton LG, Bower KJ, Adair B, Pua Y-H, Williams GP, et al. (2015) Assessment of lower limb muscle strength and power using hand-held and fixed dynamometry: a reliability and validity study. PloS one 10:e0140822