Which is an action of flexor hallucis longus?

• A. Flex the 1st toe (hallux)
• B. Flex the 2nd toe
• C. Extend the hallux
• D. Dorsiflex the ankle

Answer: (A)

The key idea here is what the flexor hallucis longus does to the big toe. This muscle runs down the back of the leg and its tendon travels under the foot to attach to the distal phalanx of the great toe, giving it the primary action of flexing the big toe at its joints (the metatarsophalangeal and interphalangeal joints). It also assists in plantarflexing the foot and supporting the arch, but its defining action is flexion of the first toe. Flexing the second toe would involve the flexor digitorum longus, not the flexor hallucis longus. Extending the hallux would be the job of the extensor hallucis longus, and dorsiflexing the ankle is done by the tibialis anterior and other anterior compartment muscles. So the action that matches flexor hallucis longus is flexion of the first toe.