Plantaris is one of the superficial muscles of the posterior crural compartment of the leg. It arises from the inferior part of the lateral supracondylar line of the femur at a position slightly superior to the origin of the lateral head of gastrocnemius. Also, it may arise from the oblique popliteal ligament. Passing inferomedially posterior to the knee joint, it becomes tendinous while passing distally to insert into the tendo calcaneus, or occasionally separately inserting into the medial side of the calcaneus.
It is innervated by the tibial nerve (S1, S2).
Plantaris acts to weakly:
- plantarflex the ankle joint
- flex the knee joint
Its function is so minimal that its long tendon can readily be harvested for reconstruction elsewhere with little functional deficit.