According to the dynamic system theories, the motions of the lower limb are coupled, and it is likely that these motions may be uncoupled/less well coordinated in the presence of patellofemoral pain (PFP). Literature also suggests that there may be differences between males and females with and without PFP. However, evidence to support this hypothesis in runners is contradictory.

To investigate differences between lower limb coordination and coordination variability between male runners with and without PFP and between female runners with and without PFP.

A cross-sectional study involving 83 runners. The female group was composed by 40 runners, 20 with PFP (mean age 27.5 years, running average of 20.1 km/week, mean duration of pain 14.6 months) and 20 without PFP (27.2 years, running average of 28.5 km/week). The male group was composed of 43 runners, 22 with PFP (28.4 years, running average of 22.5 km/week, mean duration of pain 14.4 months) and 21 without PFP (28.5 years, running average of 39.8 km/week). A 3-dimensional kinematics analysisthe femur, tibia, and foot during g a treadmill running was recorded. Vector Coding technique was used to analyze coordination and coordination variability for the femur-tibia-foot segments couplings. The couplings variables of interest were: (I) tibia internal/external rotation vs foot inversion/eversion, (II) femur internal/external rotation vs foot inversion/eversion, (III) femur adduction/abduction vs foot inversion/eversion, (IV) femur flexion/extension vs tibia flexion/extension, (V) femur adduction/abduction vs tibia adduction/abduction. Differences between males with and without PFP and between females with and without PFP were investigated using independent T tests and Mann-Whitney tests (α<0.05).

In coordination patterns – male runners with PFP were significantly different to male runners without PFP for the following couplings: (1) femur internal/external rotation vs foot inversion/eversion (p=0.031), (2) femur adduction/abduction vs foot inversion/eversion (p=0.001) and (3) femur flexion/extension vs tibia flexion/extension (p=0.005). No differences were found for female runners.

In coordination variability – males with PFP had lower variability than those without PFP for the following couplings: (1) tibia internal/external rotation vs foot inversion/eversion (p<0.001), (2) femur internal/external rotation vs foot inversion/eversion (p=0.002), (3) femur adduction/abduction vs foot inversion/eversion (p=0.012) and (4) femur flexion/extension vs tibia flexion/extension (p<0.001). No such differences were found for female runners.

According to our findings, male runners with PFP had different coordination patterns and presented lower coordination variability than those without PFP. This is in agreement with the theory that less coordination variability is indicative of a pathological coordinate state with reduced ability to adapt, which could lead to repetitive stress in the knee joint over time. On the other hand, it appears that female runners with PFP do not have alterations in coordination patters or its variability when compared with females without PFP for the couplings analyzed.

The results of this study allow for a better understanding of the movement alterations that occur in runners with PFP. Future studies should investigate whether alterations in the couplings between lower limb segments are risk factors for the development of PFP in runners.