Calcaneal tendon

The calcaneal tendon ( Achilles tendon) is the largest and strongest tendon in the human body. It is about 15 cm. long, and begins near the middle of the leg, but receives fleshy fibers on its anterior surface, almost to its lower end. It is formed by the confluence of the tendinous fibers from the gastrocnemius (medial and lateral heads) and soleus muscles. These muscle fibers twist as they descend, creating a complex, spiralized structure. The subtendon from the lateral head of the gastrocnemius typically forms the largest component at the insertion, followed by the soleus and then the medial head of the gastrocnemius.

The tendon inserts onto the posterior surface of the calcaneal tuberosity. The insertion is crescent-shaped, with significant medial and lateral projections, and the superficial fibers (mainly from the medial gastrocnemius) insert over the entire width of the inferior facet, while deeper fibers (from the soleus and lateral gastrocnemius) insert more medially and laterally on the middle facet.

The anterior fibers of the tendon, particularly those from the soleus and lateral gastrocnemius, are implicated in insertional tendinopathy.