Association between Lower Extremity Kinematics and Muscle Strength, Pain, Physical Activity level, and Functional status in Females with Patellofemoral Pain

Abstract

Background: Impaired lower extremity kinematics has beenconsidered as a contributing factor to patellofemoral pain (PFP). However, current knowledge about the correlation between lower extremity kinematics and muscle strength is very limited. This study investigated the correlation between lower extremity kinematics and muscle strength, pain, physical activity level, as well as functional status in females with PFP. Methods: Seventy-five females with PFP participated in this analytical cross-sectional study. Lower extremity kinematics, maximal isometric strength of muscles, pain severity, physical activity level, as well as subjective and objective function were assessed using a motion analysis system, a dynamometer, Visual Analog Scale, the International Physical Activity questionnaire, and the Kujala questionnaire and the step-down test, respectively. The hip and knee kinematics were determined during the initial contact and the initial phase of landing. Pearson's correlation coefficients were calculated to establish the correlation between the variables. Results: The knee rotation at the initial contact was significantly correlated with quadriceps strength (r= -0.240, p=0.038) and pain severity (r=0.268, p=0.020). Pain was significantly correlated with hamstring (r= -0.310, p=0.007) and quadriceps strength (r= -0.253, p=0.029) and the Kujala score (r= -0.346, p= 0.002). Conclusion: Our findings do not indicate a strong correlation between muscle strength and joint kinematics in females with PFP. An explanation is the presence of various subgroups of people with PFP. Future studies should focus on evaluating the correlation between the risk factors of PFP in subgroups, classified based on biomechanical, psychosocial, and anatomical characteristics.