The plantaris muscle is one of the calf muscles in the superficial posterior compartment of the leg. It is a long, thin and variably developed muscle that runs from the femur to the Achilles tendon.
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Summary
origin: posterosuperior aspect of the lateral femoral condyle and the oblique popliteal ligament
insertion: calcaneum medial or anterior to the Achilles tendon
arterial supply: sural arteries
innervation: tibial nerve
antagonist: tibialis anterior
key relationships: between the medial head of the gastrocnemius and soleus
Gross anatomy
Origin and insertion
The plantaris muscle arises from the posterosuperior aspect of the lateral femoral condyle, close to the origin of lateral head of gastrocnemius. There is often an attachment to the oblique popliteal ligament. As the plantaris crosses the posterior knee joint, it runs medially.
In the calf, it lies in between the medial head of the gastrocnemius and soleus.
Distally, the tendon has a variable insertion pattern but most commonly inserts into the calcaneum either medial or anterior to the Achilles tendon 5.
Plantaris can have variable size, but in most cases is difficult to demonstrate on routine MRI studies.
Function
Plantaris acts weakly to plantar flex the foot and flex the knee. It is considered a vestigial muscle.
Variant anatomy
In up to 10% of the population, the plantaris is absent; in a smaller number, it may be duplicated 3.
Clinical importance
Plantaris tendon can be used as a tendon graft in reconstructive surgery 5.
Related pathology
the plantaris tendon is most easily visualized when there is fluid collection in the myofascial junction between gastrocnemius and soleus, commonly secondary to an injury of the medial gastrocnemius head (tennis leg)
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