Three-Dimensional Movement of the Foot During the Stance Phase of Walking.

Cornwall MW, McPoil TG (Gait Research Laboratory, Department of Physical Therapy, Northern Arizona University, Flagstaff, Ariz), J Am Podiatr Med Assoc. 1999;89:56-66.

This study used a 3-dimensional electromagnetic motion analysis system to determine the 3-dimensional movement of the calcaneus, navicular, and first metatarsal bones relative to the tibia in 153 people (men and women; mean age=26.2 years) who were walking at self-selected speeds. The authors were interested in analyzing the sequencing of rearfoot, midfoot, and forefoot movement relative to the tibia in order to ascertain when the segments work together rather than separately during functional walking.

The authors reported multiple correlation values, which indicated sufficient between-trial consistency. Although they found that the magnitudes of movement were different for each foot segment, the authors believed that the patterns of movement were strikingly similar. Each segment was found to undergo the same pattern of dorsiflexion/plantar flexion, inversion/eversion, and external/internal rotation relative to the tibia. The correlation between eversion/inversion of each foot sensor and the external/internal rotation of the tibia were found to be extremely high.

According to the authors, the data supported the concept of interlinked "foot" inversion/eversion rather than separate subtalar or mid-tarsal inversion/eversion. They suggested that the tarsal mechanism (ie, subtalar and talocalcaneonavicular joints) had a consistent, predictable, and interdependent motion during walking. The tarsometatarsal mechanism (ie, first metatarsal and associated joints), on the other hand, did not have as strong a kinematic coupling and. therefore, produced a more independent movement. The first metatarsal bone, although similar to the navicular and calcaneus bones, was found to have a motion pattern that is independent of the 2 proximal foot segments. According to the researchers, its rapid eversion early in the stance phase illustrates the "pronation twist" of the tarsometatarsal mechanism. The study also revealed that the magnitude of the navicular bone's movement was greater than that of the calcaneus, which may highlight a specific role for the midfoot during typical foot function. The authors suggested that the traditional view of the foot functioning around a defined neutral subtalar joint positioning is not supported by current biomechanical data.

Robert Tank, PT, ATC
Orthopaedic Associates Inc
Evansville, Ind