The heel strike transient during walking in subjects with patellofemoral pain syndrome

Objectives The foot impact during the initial ground contact has been suggested to be related to pain and injury to joints. This study investigated the peak heel strike transient vertical force; its timing and the rearfoot angle relative to the tibia in the frontal plane at this time in 11 females with patellofemoral pain syndrome (PFPS) compared to 14 healthy controls. Method Subjects were examined during five walking trials across a Kistler force plate (1000 Hz). The rearfoot angle relative to the tibia was measured by attaching external markers to a tibia shell and the calcaneus using a four-camera (50 Hz) motion analysis system. Results A one-way ANOVA showed a significantly delayed appearance of the peak heel strike transient and a reduction in its magnitude in the PFPS group. PFPS subjects also exhibited a rearfoot everted posture at time of heel strike transient while the control group exhibited an inverted posture. There was no significant difference in the walking velocity between the groups. Conclusion In PFPS subjects the heel strike transient magnitude was lower and occurred significantly later which were not due to altered walking velocity. Rather, the simultaneous rearfoot everted posture may affect the heel strike transient magnitude by attenuating the impact force.