Tibialis posterior contributes to which combination of actions?

Tibialis posterior contributes to which combination of actions?

• A. Rearfoot eversion, arch lowering, tibial internal rotation
• B. Hip flexion, knee extension, toe flexion
• C. Knee flexion, ankle dorsiflexion, hip adduction
• D. Rearfoot supination, arch raising, external rotation of the lower leg relative to the foot

Answer: (D)

Tibialis posterior mainly acts to invert the foot (supinate) and plantarflex the ankle, while supporting the medial arch. When this muscle contracts, it raises the arch and stabilizes the midfoot during stance. Because its tendon crosses the medial ankle and pulls the foot into inversion, the effect is best described as rearfoot supination with arch raising, and it even contributes to external rotation of the lower leg relative to the foot as the foot becomes inverted. That combination—rearfoot supination, arch raising, and external rotation of the leg relative to the foot—captures the primary actions of tibialis posterior.

Tibialis posterior mainly acts to invert the foot (supinate) and plantarflex the ankle, while supporting the medial arch. When this muscle contracts, it raises the arch and stabilizes the midfoot during stance. Because its tendon crosses the medial ankle and pulls the foot into inversion, the effect is best described as rearfoot supination with arch raising, and it even contributes to external rotation of the lower leg relative to the foot as the foot becomes inverted. That combination—rearfoot supination, arch raising, and external rotation of the leg relative to the foot—captures the primary actions of tibialis posterior.