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Portrait of Plantaris

Anatomy · Muscles

Plantaris

The vestigial muscle with the very long tendon

Lower limb · leg, posterior compartment

Plantaris is a small, slender muscle in the calf with a short belly and an exceptionally long, thin tendon that runs between gastrocnemius and soleus to join the Achilles tendon. It is weak and is absent in roughly one in ten people. It is supplied by the tibial nerve and its tendon is often harvested for surgical grafts.

How to spot them

  • ▸Tiny belly behind the knee, lateral, with a very long thread-like tendon
  • ▸Tendon runs down between gastrocnemius and soleus, on the medial side of the Achilles tendon
  • ▸Absent in a minority of people
  • ▸Sometimes mistaken for a nerve

What to know

A calf muscle with a belly only 7–10 cm long but a very long thin tendon

Plantaris.

A muscle absent in about one person in ten

Plantaris — around 10 per cent according to Kenhub.

The tendon that runs between gastrocnemius and soleus and is often harvested for tendon reconstruction elsewhere

Plantaris.

A muscle sometimes called 'the freshman's nerve' because students mistake its tendon for one

Plantaris.

It arises from the lateral supracondylar line of the femur and the oblique popliteal ligament

Plantaris.

A weak assistant of plantarflexion and knee flexion, thought to be a vestige of a larger muscle

Plantaris.

Key ideas

  • Its slender tendon joins the Achilles tendon; rupture of the plantaris was once mistaken for a deep vein thrombosis.
  • Its tendon is used as a graft in tendon and ligament surgery because it is expendable.

Quick-fire facts

  • •Origin: lateral supracondylar line of the femur and the oblique popliteal ligament.
  • •Insertion: posterior calcaneus via the Achilles tendon.
  • •Nerve supply: tibial nerve (S1–S2).
  • •Action: weakly assists plantarflexion and knee flexion.
  • •The belly is 7–10 cm long; the tendon is long and thin.
  • •Absent in around 10 per cent of people (Kenhub).
  • •Its tendon is harvested for reconstructive surgery.

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Sources