Which muscle plantar flexes the ankle and originates from the head of the fibula and tibia?

• A. Soleus
• B. Gastrocnemius
• C. Fibularis Longus
• D. Tibialis Anterior

Answer: (A)

Plantar flexion is driven most by the soleus, a deep calf muscle that actually originates from both the fibular head and the posterior surface of the tibia. This broad origin anchors the muscle to the two bones, and its tendon merges with the gastrocnemius to form the Achilles, inserting on the heel. The soleus is the key endurance plantar flexor, active when standing and during slow, controlled pushing off the ground.

The other muscles don’t fit the origin pattern: the gastrocnemius starts above the knee from the femur, not the tibia/fibula; the fibularis longus comes from the fibula only and mainly everts the foot with a weaker plantar flexion role; the tibialis anterior runs on the front of the leg and dorsiflexes the foot rather than plantar flexing it.