The muscles that control ankle movement originate in the lower leg. They are responsible for foot and ankle movement up and down (dorsiflexion and plantar flexion) and turning in and out (inversion and eversion). The muscle bellies are located in the lower leg while the tendons travel and attach to the foot and ankle. Tendons are the part of the muscle that attaches the muscle to the bone.
In addition to movement, strong muscles provide active stability to the ankle as opposed to the passive stabilization of the ligaments. The major muscles of the ankle include the gastrocnemius and soleus (calf) muscles, which push the foot down and allow us to go up on our toes. These two large muscles join at the ankle to form the Achilles tendon.
The two peroneal muscles, longus and brevis, are located on the outside of the ankle, and push the foot down (plantar flexion) and turn it out (eversion). They also support the lateral ankle to prevent sprains. The posterior tibialis is located on the inside of the ankle, and supports the arch of the foot and helps turn the ankle in (inversion). The anterior tibialis muscle attaches to the front of the foot, and helps lift it up (dorsiflexion).
Any damage, weakness, tendonitis or tear of these muscles or tendons can have a profound effect on the function and stability of the foot and ankle. For instance, weakness of the anterior tibialis may produce a condition called foot drop. The result is a dragging of the foot producing a foot slap or tripping while walking.