Plantaris

The plantaris (Latin: musculus plantaris) is a long and slender leg muscle. It belongs to the posterior compartment of the leg muscles and is located in the superficial layer along with the gastrocnemius and soleus muscles. The plantaris consists of a short belly and a very long and thin tendon. Its tendon is so thin that it is often mistaken for a nerve during dissections. The plantaris extends from the femur and knee joint to the calcaneus.

Plantaris
OriginLateral supracondylar line of femur, oblique popliteal ligament of knee joint
InsertionPosterior surface of calcaneus (via Achilles tendon or independantly)
ActionKnee flexion, foot plantarflexion
InnervationTibial nerve (S1 - S2)
Blood supply Branches of popliteal and posterior tibial arteries

Origin

The plantaris muscle originates from the lateral supracondylar line of the femur and oblique popliteal ligament of the knee joint.

Insertion

The plantaris descends inferomedially along the medial border of the gastrocnemius muscle and inserts on the posterior surface of the calcaneus via the Achilles tendon or independently. The Achilles tendon is also known as the calcaneal tendon, and it is a common tendon for the plantaris, soleus and gastrocnemius muscles.

Action

The plantaris muscle provides foot plantarflexion at the talocrural (ankle) joint and knee flexion at the knee joint.

Innervation

The plantaris is innervated by the tibial nerve (S1 - S2) that arises from the sciatic nerve of the sacral plexus.

Blood supply

The plantaris muscle receives arterial blood supply from the branches of the popliteal artery - lateral sural and superior lateral genicular arteries. Also, it is supplied by the branches of the posterior tibial artery.