Weakness or poor function of tibialis posterior may result in which deviation?

Weakness or poor function of tibialis posterior may result in which deviation?

• A. Excessive pronation
• B. Drop foot only
• C. Jackknifing only
• D. Excessive hip extension

Answer: (A)

Weakness of tibialis posterior reduces support for the medial arch and the inverting action of the foot. When this muscle doesn’t function well, the arch can’t resist ground reaction forces during stance, causing the foot to roll inward more than normal. That inward roll is excessive pronation, often with hindfoot valgus and a flattened arch, which is exactly the deviation described. The other options don’t fit this muscle’s role: dropping the foot (loss of dorsiflexion) stems from dorsiflexor weakness, jackknifing is a knee/hip-related gait pattern, and excessive hip extension isn’t a direct result of tibialis posterior weakness.

Weakness of tibialis posterior reduces support for the medial arch and the inverting action of the foot. When this muscle doesn’t function well, the arch can’t resist ground reaction forces during stance, causing the foot to roll inward more than normal. That inward roll is excessive pronation, often with hindfoot valgus and a flattened arch, which is exactly the deviation described. The other options don’t fit this muscle’s role: dropping the foot (loss of dorsiflexion) stems from dorsiflexor weakness, jackknifing is a knee/hip-related gait pattern, and excessive hip extension isn’t a direct result of tibialis posterior weakness.