Updated November 25, 2014.

A medial gastrocnemius strain (MGS) is an injury to the calf muscle in the back of the leg.

A muscle strain occurs when the muscle is stretched too far, which causes tears to occur within the muscle. A calf strain occurs when the muscle in the back of the leg sustains this type of injury.

The calf is made of three major muscles, the medial and lateral gastrocnemius and the soleus muscle. The most commonly injured muscle when a calf strain occurs is an injury to the medial gastrocnemius muscle.

The symptoms of a medial gastrocnemius strain include pain in the back of the leg (more on the inner side), swelling and bruising.

Treatment of a medial gastrocnemius strain can usually be accomplished with ice, rest, and activity modifications.

Also Known As: MGS, calf strain, gastroc strain