Author(s): SHI, H., HUIJUAN, S., YUANYUAN, Y., YULIN, Z., HANJUN, L., HUI, L., Institution: BEIJING SPORT UNIVERSITY, Country: CHINA, Abstract-ID: 2444

INTRODUCTION:
Patellofemoral pain (PFP) is a prevalent overuse injury in runners. While altered lower limb biomechanics are considered primary risk factors, most existing studies utilize cross-sectional designs that assess patients who are already in pain. This makes it difficult to distinguish whether observed biomechanical abnormalities are the cause of the injury or compensatory strategies resulting from pain. To address this gap, this study aimed to identify biomechanical risk factors by analyzing the pre-pain phase during a continuous 5 km run, comparing runners with PFP to healthy controls.
METHODS:
Seventeen runners with PFP and 17 healthy controls, matched for sex, age, and weekly running distance, participated in the study. All participants performed a continuous 5 km running test. Kinematic and kinetic data were collected every 1 km using a markerless motion capture system (Theia3D) and force plates. For the PFP group, the pre-pain phase was defined as the kilometer immediately preceding the first report of clinically meaningful pain (VAS score >= 2). Data from the corresponding kilometer in the matched control group were used for comparison. Independent t-tests or Mann-Whitney U tests were used to analyze differences in peak joint angles, moments, angular impulses, and joint work during the stance phase.
RESULTS:
In the pre-pain phase, PFP runners exhibited distinct biomechanical deficits compared to controls. At the knee joint, PFP runners demonstrated a significantly lower peak adduction moment (p=0.014) and a higher coronal plane net angular impulse (p=0.041). At the ankle joint, PFP runners showed significantly higher net angular impulses in the sagittal (p=0.001), coronal (p=0.006), and transverse (p=0.001) planes. Furthermore, PFP runners exhibited reduced ankle peak inversion (p=0.030) and internal rotation moments (p=0.007), but increased external rotation moments (p=0.027). No significant differences were found in hip joint kinetics or angular impulses.
CONCLUSION:
PFP runners show decreased adduction moments and increased cumulative abduction loads. This is accompanied by excessive dynamic output at the ankle and altered rotational control. These findings suggest deficits in ankle control may transfer excessive loads to the knee, contributing to the development of PFP. Interventions for PFP should consider targeting ankle-knee coordination and strengthening to mitigate these pre-symptomatic risk factors.