In the open kinetic chain midtarsal joint, which axis is pronated?

In the open kinetic chain midtarsal joint, which axis is pronated?

• A. Longitudinal axis
• B. Oblique axis
• C. Both axes
• D. Neither axis

Answer: (B)

Pronation of the midtarsal joint in an open chain happens as a rotation about the oblique axis. This axis runs from plantar-medial to dorsal-lateral through the midfoot, so rotation around it produces the tri-planar combination of eversion, abduction, and dorsiflexion that characterizes midfoot pronation when the foot is not fixed to the ground. The longitudinal axis would imply a different, less coupled motion, not the typical multi-directional pronation pattern seen in open-chain movement. So, the oblique axis best explains why pronation occurs in this scenario.

Pronation of the midtarsal joint in an open chain happens as a rotation about the oblique axis. This axis runs from plantar-medial to dorsal-lateral through the midfoot, so rotation around it produces the tri-planar combination of eversion, abduction, and dorsiflexion that characterizes midfoot pronation when the foot is not fixed to the ground. The longitudinal axis would imply a different, less coupled motion, not the typical multi-directional pronation pattern seen in open-chain movement. So, the oblique axis best explains why pronation occurs in this scenario.