Chronic plantar fasciitis reduces rearfoot to medial-forefoot anti-phase coordination.

Abstract

It is commonly assumed that abnormal foot biomechanics cause plantar fasciitis; however, this assumption is not well supported. In this study, we investigated rearfoot to medial-forefoot coordination of healthy and plantar fasciitis individuals. We hypothesized that chronic plantar fasciitis individuals would exhibit greater intersegmental rearfoot to medial-forefoot anti-phase coordination and greater coordinative variability than a healthy cohort. Twenty-two individuals with chronic plantar fasciitis (symptomatic mean 4.5 years) and 22 healthy individuals participated. Three-dimensional kinematics of the rearfoot and medial forefoot segments were captured using reflective markers for walking trials. After resolving rearfoot and medial-forefoot segment angle data, a modified vector coding method was used to compute coupling angles, anti-phase movements, and coordinative variability. Compared to healthy individuals, individuals with plantar fasciitis exhibited fewer anti-phase movements (frontal plane: P = 0.003, effect size = 0.38). No group differences were detected in coordinative variability magnitude (sagittal, frontal, transverse, respectively: P = 0.99, 0.72, 0.86; effect sizes = 0.00, 0.12, 0.04). There were significant main effect differences in coupling variability between stance periods (P < 0.0001). Contrary to our hypothesis, these data suggest that a relative reduction of rearfoot to medial-forefoot anti-phase movements with a chronic plantar fasciitis injury indicates a coordinative deficit, and that a greater frequency of anti-phase movements is associated with healthy foot function. Pain, guarding, and/or the state of chronic injury may be impairing fluid inter-segmental motion. Although no group differences were found in coordinative variability, this variability increased around transitions between loading, weight acceptance, and propulsive phases of gait.