The Achilles tendon is the strongest and largest tendon in the body. It is a tendinous structure (attaches muscle to bone) that forms from a combination of the gastrocnemius and soleus muscles located in the calf. The tendon attaches to the heel bone (calcaneus) and causes the foot to push off (plantar flex) when the calf muscles tighten. The tendon is necessary for normal walking, running, and jumping. Athletic and traumatic injuries to the Achilles tendon are common and can be disabling.