Which structure exhibits triplanar motion but does supinate and pronate?

Which structure exhibits triplanar motion but does supinate and pronate?

• A. First ray
• B. Talus
• C. Navicular
• D. Calcaneus

Answer: (A)

The first ray is the structure that can move in three planes and also drive forefoot pronation and later forefoot supination. It consists of the first metatarsal and medial cuneiform, and its joints allow sagittal (dorsiflexion/plantarflexion), frontal (inversion/eversion), and transverse (abduction/adduction) motions. This tri-planar mobility lets the medial column adapt during stance and transition into propulsion. As the foot goes from loading to push-off, the first ray contributes to forefoot pronation by permitting abduction and eversion, then helps form a rigid lever through a coordinated supination (inversion/adduction) of the forefoot for propulsion. The other structures don’t combine true tri-planar mobility with a principal role in forefoot pronation and supination to the same extent.

The first ray is the structure that can move in three planes and also drive forefoot pronation and later forefoot supination. It consists of the first metatarsal and medial cuneiform, and its joints allow sagittal (dorsiflexion/plantarflexion), frontal (inversion/eversion), and transverse (abduction/adduction) motions. This tri-planar mobility lets the medial column adapt during stance and transition into propulsion. As the foot goes from loading to push-off, the first ray contributes to forefoot pronation by permitting abduction and eversion, then helps form a rigid lever through a coordinated supination (inversion/adduction) of the forefoot for propulsion. The other structures don’t combine true tri-planar mobility with a principal role in forefoot pronation and supination to the same extent.