Sagittal plane kinematics of the foot during passive ankle dorsiflexion

Measurement of ankle joint dorsiflexion is an essential examination technique that needs to be performed prior to prescription of foot orthoses since the presence or absence of ankle equinus will affect the design of such devices. The purpose of this study was to investigate the effect of foot posture on sagittal plane kinematics of various foot segments during passive dorsiflexion.

Comparative repeated measures design.

To determine the effect of foot posture on inter segmental kinematics during passive dorsiflexion.

An optoelectronic movement analysis system was employed to collect kinematic data. A validated marker set (Oxford Foot Model) was applied to 16 subjects (12 males, 4 females) with a mean age of 35.5 years (range 20-56 years), who provided informed consent. An upward force was applied to the forefoot until maximum resistance. Sagittal movement of the hindfoot and forefoot segments along with the whole foot movement were analyzed in the pronated, neutral and supinated foot postures.

While maximum foot dorsiflexion angle showed a significant difference between the three postures (p = 0.000) the actual recorded difference between the neutral and supinated postures was only 2.49°. For the hindfoot and forefoot segments, mean angle range of movement for the pronated foot posture was significantly higher than the other foot postures. The forefoot to hindfoot angle demonstrated a significant (p = 0.005) increase during dorsiflexion between the pronated and supinated postures. These results indicate that during passive dorsiflexion, the forefoot travels through a greater degree of movement than the hindfoot.

While the maximum foot dorsiflexion angle differs significantly between the pronated and supinated foot postures, hindfoot movement also varies significantly between foot postures. Furthermore, the forefoot to tibia angle travels through a greater range than the hindfoot to tibia angle, in all three foot postures. The hindfoot to forefoot angle does not remain constant during passive dorsiflexion, but increases upon application of a dorsiflexing force, indicating that the forefoot movement cannot be eliminated completely by placing the foot in any particular posture.