A strain is an injury to a muscle or a tissue connecting muscle to bone, called a tendon. Strains often happen in the lower back and in the muscle in the back of the thigh. Minor injuries may only overstretch a muscle or tendon, while more-serious injuries may involve partial or complete tears in these tissues.

Symptoms vary widely, depending on the seriousness of the injury. Symptoms include pain, swelling, muscle spasms and limited ability to move the muscle.

Strains are treated with the R.I.C.E. approach — rest, ice, compression and elevation. A health care professional may recommend treatment with pain relievers, bracing or splinting. For some injuries, such as a torn tendon, surgery may be recommended.