Tendon of plantaris muscle

The distal tendon of the plantaris muscle is a long, slender structure arising from the distal muscle belly, which typically originates at the lateral supracondylar line of the femur and the knee joint capsule. The tendon courses distally between the gastrocnemius and soleus muscles, running along the medial aspect of the posterior leg. It is characterized by its considerable length and narrow width, often described as "cord-like" or "ribbon-like".

Distally, the tendon demonstrates significant anatomical variability in its course and insertion. The most common pattern is a fan-shaped insertion onto the medial aspect of the calcaneal tuberosity, adjacent to or blending with the medial border of the Achilles (calcaneal) tendon. However, multiple insertion types have been described, including direct insertion into the calcaneus, blending with the Achilles tendon, insertion into the crural fascia, or even into the tarsal canal flexor retinaculum.