Ultrasound is well suited to evaluate a wide variety of abnormalities involving skeletal muscle, including traumatic injuries, inflammatory or infectious myositis, atrophy, and tumors. Ultrasound can accurately localize and characterize a lesion, or grade the severity of injury. The unique ability of ultrasound to assess the dynamic function of muscles on the real-time or perform Doppler evaluation of vascularity provides insights that are not readily obtained with other imaging modalities. With ultrasound, image-guided biopsy can be performed in conjunction with a diagnostic evaluation. This article presents a pictorial review of lesions and abnormalities involving skeletal muscles, and discusses characteristic findings, classifications, and imaging methods.