plantarflexor

Plantarflexor refers to a muscle or group of muscles that plantarflex the foot at the ankle, meaning they move the sole downward away from the shin. The primary plantarflexors are located in the posterior compartment of the leg and include the gastrocnemius and soleus, which together form the triceps surae, with the plantaris often regarded as a small accessory muscle. These muscles converge to form the Achilles (calcaneal) tendon, which inserts on the posterior calcaneus. Contraction elevates the heel off the ground, enabling toe standing and the propulsive push-off used in walking and running.

Anatomy and innervation: The major plantarflexors are innervated mainly by the tibial nerve. Blood supply comes from the posterior tibial artery. The gastrocnemius crosses both the knee and ankle, while the soleus crosses only the ankle. The plantaris, when present, lies between these muscles. Together, they power plantarflexion through the Achilles tendon.

Other muscles that assist plantarflexion include the deeper posterior muscles such as tibialis posterior, flexor digitorum longus, and flexor hallucis longus, which also aid in toe flexion and arch support. The fibular (peroneal) muscles contribute to plantarflexion to a lesser extent and help with foot positioning and eversion.

Clinical relevance: Adequate plantarflexor strength is essential for gait, jumping, and balance. Common problems include Achilles tendon injuries (rupture or tendinopathy), calf strains, and, less commonly, nerve or tendon pathology that reduces plantarflexion. Clinical assessments may involve testing plantarflexion strength and, in suspected rupture, the Thompson test, where diminished plantarflexion suggests an Achilles tendon rupture.