Muscle injuries are common and often occur during sport or training. The sonographic and magnetic resonance (MR) imaging appearance of muscle injures help to categorize the degree of muscle injury and when the athlete can return to play. The recent advances in ultrasound technology producing images of exquisite detail allow diagnosis of muscle injury with similar accuracy as MR imaging. Muscle injury may be divided into acute and chronic pathology, with muscle strain injury the most common clinical problem presenting to sports physicians. This article reviews the MR Imaging and ultrasound appearance of muscle injuries ranging from acute to chronic injuries, as well as the appearance of normal healing and the complications that can occur from muscle strain injuries.