Three-dimensional kinematics of the forefoot, rearfoot, and leg without the function of tibialis posterior in comparison with normals during stance phase of walking

Background. Many studies have shown that lack of functional activity of tibialis posterior leads to changes in the longitudinal arch and affects the motion of the foot. A quantitative description of the affects on the motion of the foot in detail has not been reported. Objective. To describe three-dimensional motion of the leg, rearfoot and forefoot with tibialis posterior dysfunction during stance phase of walking in comparison with normals. This study compared one case without the function of tibialis posterior with the ensemble average of 10 normals (five males, five females). Methods. Subjects with 10, 12 mm retroreflective markers placed on their right leg, rearfoot and forefoot, performed five trials of walking at self-selected speed on a 10 m walkway. A four-camera three-dimensional motion analysis system and a synchronized force platform were used to record three-dimensional motions of the segments and force variables during stance phase of walking. Results. The patterns and range of motion of the rearfoot relative to the leg, and the forefoot relative to the rearfoot demonstrated some differences between the tibialis posterior dysfunction case and normals. Most of the major differences occurred from just prior to heel-off through to toe-off, the period when a stable arch would be required. Conclusion. The observed differences in the three-dimensional foot motions of the tibialis posterior dysfunction case compared with normals during walking were consistent with the expected mechanical consequences of a foot without the function of tibialis posterior. The one exception was the inversion of the rearfoot which remained normal.