Although most muscle injuries in the athlete are diagnosed clinically, MR imaging is an excellent noninvasive diagnostic adjunct to clinical examination, which allows the site and severity of muscle injury to be assessed accurately, influencing therapy and overall outcome. There has been a rapid expansion in the clinical use of MR imaging during the past decade. MR imaging conveys unparalleled anatomic resolution and high sensitivity in the detection of acute and chronic muscle abnormalities. This article discusses the spectrum of muscle injuries, emphasizing the important role of MR imaging in their diagnosis and management.