Equinus foot deformity in this context is caused by which condition?

• A. Absence of dorsiflexion
• B. Absence of plantarflexion
• C. Absence of inversion
• D. Absence of eversion

Answer: (A)

Equinus refers to a downward, plantarflexed position of the foot at the ankle. This deformity arises when the ability to dorsiflex the ankle is absent or severely limited, so the foot cannot be brought upward toward the shin and remains tipped downward. In conditions like myelomeningocele, weakness or paralysis of the dorsiflexor muscles (like tibialis anterior) can lead to this loss of dorsiflexion, resulting in an equinus foot posture.

If plantarflexion were absent, the foot would have trouble pointing downward, which would not produce the classic equinus posture. Inversion and eversion involve turning the sole of the foot inward or outward and don’t determine the sagittal-plane ankle position that defines equinus.