Association of altered frontal plane kinematics and physical activity levels in females with patellofemoral pain

Background: Females with patellofemoral pain (PFP) present with altered frontal plane kinematics, decreased physical activity, and elevated psychological features. However, the relationship between these factors has not been evaluated. Research Question: Does a relationship exist between frontal plane kinematics, physical activity levels, and fear avoidance beliefs in females with PFP. Methods: 16 females with PFP (Age = 23.2 +/- 4.9years; Height = 166.1 +/- 5.9 cm; Mass = 66.3 +/- 13.5 kg) completed a 3-D biomechanical assessment during a single leg squat, step-down, and jogging task. Physical activity was collected with an activity monitor over 2-weeks and the Fear Avoidance Belief Questionnaire physical activity subscale was used to assess fear avoidance beliefs. Frontal plane kinematics were correlated with physical activity and fear avoidance, with significant variables included in a multiple regression. Results: Significant correlations were identified between physical activity and single leg squat hip adduction (r= - 0.626, p = 0.01), step-down knee abduction (r= - 0.783, p < 0.001) and jogging hip adduction (r= - 0.639, p = 0.008). Step-down knee abduction predicted activity level and accounted for 61% of the total variance. Correlations between fear avoidance belief and single leg squat hip adduction (r = 0.477, p = 0.049), step-down knee abduction (r = 0.644, p = 0.007), jogging knee abduction (r = 0.558, p = 0.025), and jogging hip adduction (r = 0.557, p = 0.025) were also identified. Knee abduction during the step-down and single leg squat hip adduction accounted for 37.5% of the variance in the Fear Avoidance Belief Questionnaire. Significance: Altered frontal plane kinematics during step-down and jogging provide insight for clinicians to identify females with patellofemoral pain that may be less physically active, while step-down and squatting kinematics related to fear avoidance beliefs. While these relationships were found, it is essential to identify the underlying mechanism for this activity modification so clinicians and researchers can evaluate successful interventions.