Subtalar joint movement: clinical and computed tomography scan correlation

The purpose of this study was to compare subtalar motion measured externally (representing clinical assessment) with subtalar motion measured by computed tomography (CT), in normal individuals. Ten recreationally active subjects (20 lower extremities), aged 20 to 35 years with no lower extremity pathologic condition, were involved in the study. External subtalar inversion and eversion was assessed using a goniometer. By overlaying CT images of the subtalar joint in inversion and eversion on neutral images, angular subtalar motion was measured directly. Subtalar motion measured by CT ranged from 5 degrees to 16 degrees (mean, 11 degrees). External subtalar motion ranged from 39 degrees to 54 degrees (mean, 46 degrees), overestimating CT measurement of subtalar motion by approximately three-fold. This discrepancy is probably secondary to soft tissue motion and talocrural motion that is not isolated from subtalar motion at clinical examination. This solidifies our belief that clinical assessment of subtalar motion should no longer be used to determine or document the measurement of subtalar motion.