Sex-specific Knee Biomechanics Associated With Patellofemoral Pain In Amateur Runners During Running

Abstract

Patellofemoral Pain (PFP) is a common injury among runners. The mechanisms of sex differences associated with lower extremity biomechanics in PFP are still unclear. PURPOSE: To determine the differences in knee biomechanics between male and female amateur runners with PFP and without PFP in running task. Further, to determine the sex-specific biomechanical factors associated with the development of PFP. METHODS: 15 male and 10 female amateur runners aged 18 to 40 years with PFP were screened and enrolled in PFP group, 25 healthy amateur runners matched with the PFP group in sex, age, and running experience were recruited as control group. PFP group was tested running with and without knee pain (PFP with pain and PFP without pain groups), while control group performed one running test (running speed = 4.0 ± 0.3 m/s). Knee pain in PFP group was eliminated by decreasing the volume of running. Knee kinematics and kinetics during landing phase of running were reduced from reflective marker coordinates and ground reaction force data, as well as compared among groups and between sexes. RESULTS: Peak knee valgus angle of running in PFP group with pain (male: 3.2 ± 4.2°, female: 4.8 ± 4.9°, P = 0.001) and control group (male: 1.9 ± 2.7°, female: 3.8 ± 3.0°, P = 0.001) were significantly lower compared to PFP group without pain (male: 4.5 ± 4.3°, female: 7.9 ± 3.1°). Peak knee external rotation moment of running in PFP group with pain (male: 0.021 ± 0.008 BW × BH, female: 0.019 ± 0.006 BW × BH, P = 0.019) and control group (male: 0.020 ± 0.006 BW × BH, female: 0.017 ± 0.006 BW × BH, P = 0.001) were significantly lower compared to PFP group without pain (male: 0.024 ± 0.009 BW × BH, female: 0.022 ± 0.008 BW × BH). Peak knee flexion angle of running in PFP group without pain (48.8 ± 5.6°) was significantly greater compared to control group for male participants (46.0 ± 3.6°, P = 0.008). CONCLUSIONS: Decreased knee valgus angle and external rotation moment in running appeared to be compensations to avoid pain when amateur runners with PFP were running with pain, and increased knee valgus angle and external rotation moment might be biomechanical factors associated with the development of PFP. Increased knee flexion angle in running may be another critical biomechanical factor associated with the development of PFP for male amateur runners.