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 which runs from the femur to the Achilles tendon.

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 obliquely from the lateral to medial.

In the calf, it lies in between the medial head of the gastrocnemius and soleus.

Distally, the tendon inserts into the medial aspect of the Achilles tendon.

Plantaris can have variable size, but in most cases is difficult to demonstrate on routine MRI studies. 

Plantaris acts weakly to plantar flex the foot and flex the knee. It is considered a vestigial muscle, and can be used by the orthopaedic surgeons as graft in reconstructions.

In up to 10% of legs plantaris is absent, and in a smaller number it may be duplicated 3.

It is most easily visualised when there is fluid collection in the myofascial junction between gastrocnemius and soleus, commonly secondary to strain of the medial head of gastrocnemius (tennis leg).

Anatomy: Lower limb
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Article information

rID: 6012
Section: Anatomy
Synonyms or Alternate Spellings:
  • Plantaris Muscle

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Cases and figures

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    Figure 1: plantaris muscle
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    Figure 2: superficial leg muscles
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