Plantaris as a cause of midsubstance Achilles tendon pain

The plantaris muscle is often dismissed as a small, vestigial muscle, however an injury to this structure should actually be included in the differential diagnosis of the painful calf or Achilles tendon.

Injury to the plantaris on its own, or in association with concurrent injuries of the knee can present a diagnostic challenge. The plantaris muscle consists of a small, thin muscle belly, and a long thin tendon that forms part of the posterosuperficial compartment of the calf. 

muscle render 1.jpg

Location of the plantaris in the popliteal fossa: a) demonstrates plantaris (P) deep to the lateral head of the gastroc b) demonstrates the plantaris (P) with the gastroc removed. The plantaris is superficial to the popliteus muscle.

Together with the gastrocnemius, and soleus, they are collectively referred to as the triceps surae muscle. The muscle originates from the lateral supracondylar line of the femur just superior and medial to the lateral head of the gastrocnemius muscle as well as from the oblique popliteal ligament in the posterior aspect of the knee. The muscle ranges from 7 to 13 cm long varying highly in both size and form when present.

In about 7% of the population, the plantaris is completely absent.

Simon Bartold
Director of Bartold Clinical