Patellofemoral Pain Lead to Greater Joint Motion and Coordination Variability during a Prolonged Run

PURPOSE: To examine effects of patellofemoral pain (PFP) on lower extremity kinematics and joint coordination variability during a prolonged run. METHODS: Participants included 12 college-aged female runners in two groups: 6 with PFP and 6 healthy (CON), matched by age, height and body mass. Kinematic data was captured at sampling of 100Hz. Sixteen anatomical retroreflective markers, 7 tracking clusters, were placed on the participants’ lower extremities for the static trial. Only the clusters remained for the running trial. Participants ran at a self-selected pace on a treadmill until they met exertion or pain criteria. Data for 20 steps from 3 time points (beginning, middle, and end) of the run were processed. Kinematic variability was assessed for each participant by calculating the standard deviation (SD) of peak knee flexion, internal rotation, and adduction angle and their velocities over 20 steps captured at the 3 time points. Continuous relative phase (CRP) mean values were calculated from normalized phase plots for coordination relationships between knee horizontal plane motion and hip sagittal, frontal, horizontal and ankle frontal plane motion. Coordination variability was calculated as the CRP coupling SD over 100% of stance for each time point for each participant. Statistical comparisons were assessed through a 2 (PFP vs CON) x 3 (beginning, middle, and end) repeated measures ANOVA. RESULTS: There was an increase in variability for peak knee adduction angle (PFP: 0.6, 0.6, 0.14; CON: 0.5, 0.9, 0.6, group X time interaction: p \u3c.05), peak knee adduction velocity (PFP: 13.1, 14.7, 30.7; CON: 20.4, 13.1, 15.6, group X time interaction: p \u3c.05), hip flexion / knee rotation CRP (PFP: 73.2, 56.7, 125.5; CON: 70.2, 70.0, 57.3, group X time interaction: p \u3c.05), and knee rotation / rearfoot eversion CRP (PFP: 35.4, 47.2, 90.5; CON: 30.7, 27.6, 25.1, group X time interaction: p \u3c.05) over time for the PFP group compared with healthy. CONCLUSIONS: The increase in joint kinematics and coordination variability over time observed only in the PFP group may indicate that pain and exertion experienced by the PFP group may decrease movement control towards the end of a prolonged run