The real-time imaging feature of sonography is of particular interest because some disorders of muscles, tendons and joints are better- or in some cases, only-seen dynamically, that is, during motion of the extremity, muscle contraction, probe compression, or position change of the patient. Sonography should be the first imaging modality used to evaluate snapping hip. Dynamic sonographic studies can help to identify the structure involved in extra-articular snapping hip by showing the abnormal displacement of this structure with hip motion. Dynamic sonography has an important role in diagnosis of medial and lateral snapping knee syndrome during knee motion. Dynamic sonography, or imaging during ankle joint motion, can aid in the evaluation of peroneal tendon tears, transient subluxation, and dislocation