plantarflex

Plantarflex, or plantarflexion, is the movement of the foot at the ankle joint that points the toes downward and raises the heel, so the sole moves toward the ground. The action is produced by the plantarflexor muscles in the posterior compartment of the lower leg, most notably the gastrocnemius and soleus, which together form the triceps surae.

Other muscles contribute to plantarflexion, including the plantaris, tibialis posterior, flexor digitorum longus, and flexor hallucis longus. These muscles assist especially when the toes are flexed or the foot is in a more inverted position. The primary action occurs at the talocrural (ankle) joint, with additional involvement of the subtalar and midfoot joints during gait and balance.

In locomotion, plantarflexion provides the push-off phase that propels the body forward. Clinically, it is assessed by manual muscle testing: with the knee extended, plantarflexion tests largely reflect gastrocnemius strength, while with the knee flexed, soleus contribution is emphasized. Normal ranges for plantarflexion are commonly cited around 40–50 degrees, with dorsiflexion typically about 15–20 degrees.

Injury or disease affecting the plantarflexors, such as an Achilles tendon rupture or tibial nerve damage, can weaken plantarflexion and impair gait. Plantarflexion strength and power are important for activities such as running, jumping, and standing on tiptoes. The term can also be used to describe movements or actions of devices designed to mimic this motion.