Lower leg, posterior superficial view.
The calf muscles are muscles extending from the back of the knee to the heel. The gastrocnemius starts behind the knee and forms the bulky part of the calf. Under it is the soleus, which is longer and thinner than the gastrocnemius and starts lower down from the back of the tibia (shin). These muscles, together with the planatarius muscles, join to form the Achilles tendon, which connects them to the heel.
Contraction of the calf muscles pulls the heel up to produce a springing movement through the toes. This movement is important in walking, running, jumping, and hopping.
Disorders of the calf muscles
Pain can occur because of cramp, sciatica (inflammation of the sciatic nerve) or, more rarely, deep vein thrombosis. The calf muscles may be affected by claudication (a cramp-like pain brought on by walking and quickly relieved by rest).