Which muscle has its origin at the soleal line and the proximal posterior tibia?

• A. Gastrocnemius
• B. Soleus
• C. Tibialis posterior
• D. Flexor digitorum longus

Answer: (B)

The muscle in question is the one that starts at the soleal line on the posterior surface of the tibia, along with the proximal posterior tibia (and adjacent fibula). This placement is characteristic of the soleus, a powerful plantar flexor that sits deep in the posterior leg and, with the gastrocnemius, forms the Achilles tendon. The other muscles have different origins: the gastrocnemius comes from the femoral condyles near the knee; tibialis posterior originates from the posterior surfaces of the tibia and fibula plus the interosseous membrane; and flexor digitorum longus arises from the posterior tibia below the soleal line.