Sonography of the quadriceps muscle: Examination technique, normal anatomy, and traumatic lesions.

Lesions of the quadriceps muscle (QM) are frequently seen by sonographers, and in most cases they are the result of sports-related trauma. An accurate assessment of the severity of the lesion is essential, particularly when the patient is a professional athlete. In most cases, careful history-taking and a thorough physical examination are sufficient for making the diagnosis and indicating the most suitable imaging studies for each case. Clinical assessment alone, however, may not be sufficient for distinguishing contusions from small, partial tears or for estimating the size of a tear. Therefore, at least in patients who are professional athletes, imaging studies are necessary to plan appropriate therapy that will allow prompt functional recovery. Muscles cannot be visualized with conventional radiography, but it is used routinely in prepubertal patients because it can detect apophyseal detachments, which are the most frequent muscle lesion in this age group. Radiography is also useful when myositis ossificans is suspected. Magnetic resonance imaging, thanks to its excellent tissue contrast, allows simultaneous assessment of muscle, joint, and bone planes. It remains a second-line study due to its high cost and relatively low availability. It is also associated with various contraindications, the most important of which is the presence of a cardiac pacemaker. Ultrasonography has a number of advantages, including widespread availability, absence of contraindications, and low cost. It can also be used for dynamic studies of the muscle during contraction and relaxation, and if doubts arise, scans can easily be obtained of the contralateral muscle for comparison purposes. These qualities make it an excellent tool for follow-up of patients with QM lesions, when follow-up is necessary. This article reviews the anatomy of the QM, the technique used for standard ultrasound examination of this muscle, its normal appearance on ultrasound, and the sonographic characteristics of the most common traumatic lesions that affect it.