A sprain refers to an injury to a ligament-one of the tough, fibrous cords that act as tethers to hold the bones together at the joint. Sprains occur at the joints when the adjacent bones are twisted or pushed too far. The ligaments can stretch and even tear, causing pain and loss of function. The most common joints to experience sprains are the knee, ankle, shoulder, and those in the fingers.

A strain refers to a muscle injury. As such, strains usually occur away from the joint, in the muscle tissue. The most commonly injured muscles are the hamstring at the back of the thigh and the gastrocnemius, or calf muscle. Athletes commonly suffer both sprains and strains.