The talocrural joint functions in the motion of dorsiflexion and plantarflexion. Due to triplanar motion at this joint, what other motion occurs with dorsiflexion?

Question

a. Abduction
b. Adduction
c. Inversion
d. Eversion

Answer 1

ANS: A
The ankle joint is considered to be triplanar because its axis for dorsiflexion-plantarflexion crosses all three planes. The ankle joint axis passes through the malleoli of the tibia and fibula. Rather than being a true coronal axis, the ankle joint axis is rotated laterally about 20 ° to 30 °. It is also inclined downwardly about 10 ° on the lateral side. The laterally rotated location of the axis gives the foot its apparent toe-out stance. An ankle joint axis rotated laterally in excess of 20 ° to 30 ° from the frontal plane indicates the existence of lateral tibial torsion. Less than 20 ° to 30 ° of inclination would be considered medial tibial torsion. Although not immediately obvious from examining the inclination, the orientation of the ankle joint axis results in dorsiflexion of the ankle being accompanied by movement of the tibia medially on the fixed foot (or movement of the foot laterally on the tibia when the distal lever is free). With this triplanar motion, there is also an abduction motion seen with dorsiflexion, and adduction accompanies plantarflexion.