Distinguishing structures seen on ultrasound can be a difficult task for novice ultrasonographers; however, most musculoskeletal tissues have a characteristic echogenic pattern when viewed in orthogonal planes. As stated earlier, it is important to describe structures seen on ultrasound in terms of echogenicity, echotexture, susceptibility to anisotropy, compressibility, and presence or absence of blood flow. The normal appearance of several soft tissues is described below and summarized in Table 39–1.
Table 39–1Normal ultrasonographic characteristics of common structures. |Favorite Table|Download (.pdf) Table 39–1 Normal ultrasonographic characteristics of common structures.
|Structure ||Echogenicity ||Transverse Appearance ||Longitudinal Appearance ||Susceptibility to Anisotropy ||Compressible ||Doppler Flow |
|Tendons ||Hyperechoic ||“Broom end” ||Fibrillar ||High ||No ||Negative |
|Ligaments ||Hyperechoic ||“Broom end” ||Fibrillar ||High ||No ||Negative |
|Nerves ||Mixed ||“Honeycomb” ||Fascicular ||Mild ||No ||Negative |
|Muscles ||Mixed ||“Starry night” ||Feathery ||Mild ||Yes ||Negative |
|Vessels ||Anechoic ||N/A ||N/A ||N/A ||Yes ||Positive |
|Bone ||Hyperechoic ||Linear, smooth ||Linear, smooth ||— ||No ||Negative |
Tendons exhibit a fibrillar pattern when imaged longitudinally and a “broom end” pattern when imaged transversely. As these tissues are typically hyperechoic and highly susceptible to anisotropy, it is important to focus the ultrasound waves perpendicularly when imaging tendons. Tendons are not compressible and do not normally have any blood flow seen on Doppler examination. Longitudinal and transverse views of various tendons are shown in Figures 39–1,Figures 39–2,Figures 39–3,Figures 39–4,Figures 39–5,Figures 39–6,Figures 39–7,Figures 39–8,Figures 39–9,Figures 39–10,Figures 39–11,Figures 39–12,Figures 39–13,Figures 39–14,Figures 39–15,Figures 39–16,Figures 39–17, and 39–18.
Longitudinal view of the supraspinatus tendon shown underneath the deltoid muscle and the bursa.
Longitudinal view of the supraspinatus tendon with an anechoic area in the middle of the tendon representing a tear.
Transverse view of the supraspinatus tendon. (BICEPS TRANS, transverse biceps tendon.)
Transverse view of the supraspinatus tendon with a hypoechoic area representing a tear.
View of the infraspinatus tendon in the longitudinal view.
Longitudinal view of the subscapularis as it inserts onto the lesser tubercle (LT).
Transverse view of the biceps tendon between the greater and lesser tubercles.
Longitudinal view of the biceps tendon insertion and the brachial vessel running with the tendon.
Comparison of common wrist flexor origins. The tendon originating from the left medial epicondyle has a mixed echotexture compared with the tendons from the right medial epicondyle.
Longitudinal view of the common extensor tendons as they originate from the lateral epicondyle.
Longitudinal view of the distal quadriceps tendon as it inserts onto the patella (PAT). The suprapatellar recess is also labeled. (FP, fat pad.)
Transverse view of the second through fourth wrist extensor tendon compartments. (ECRB, extensor carpi radialis brevis; ECRL, extensor carpi radialis longus; EDC/EIP, extensor digitorum communis/extensor indicis proprius; EPL, extensor pollicis longus.)
Longitudinal view of the proximal patella tendon.
Longitudinal view of the distal patella tendon with the infrapatellar bursa seen deep to the patella tendon.
Longitudinal view of the distal Achilles tendon (ACH) as it inserts onto the calcaneus.
Longitudinal view of a thickened Achilles tendon (ACH) with mixed echogenicity proximal to its insertion onto the calcaneus. This is representative of a tendinopathy.
Transverse view of the distal Achilles tendon (ACH) as it inserts onto the calcaneus. The retrocalcaneal (RETROCALC) bursa is identified in the image.
Short axis comparison of left and right, midportion plantar fascia (PF). Compared with the asymptomatic left side, notice the large area of hypoechogenicity of the symptomatic right PF. This represents a tear versus chronic changes. (asx, asymptomatic; SYX, symptomatic.)
P: Ultrasound of tendons. Imaging 2002;14:223–228.
L. Tendon and nerve sonography. Radiol Clin North Am 1999;37:691–711.
Ligaments have a similar appearance to tendons. When imaged longitudinally, they have the appearance of a fibrillar pattern, and when imaged in the transverse plane, a “broom end” appearance. Compared with tendon fibers, the fibers in ligaments appear less compact. When scanning tissues, ligaments can be distinguished from tendons by the fact that ligaments will be seen originating and terminating on bony structures. Ligaments are hyperechoic and are susceptible to anisotropy. Similar to tendons, these structures normally lack any blood flow and are not compressible. Longitudinal and transverse views are shown in Figures 39–19,Figures 39–20,Figures 39–21,Figures 39–22, and 39–23.
Ulnar collateral ligament (UCL) seen connecting the distal humerus to the ulna.
Longitudinal view of the medial collateral ligament (MCL).
Transverse view of the proximal medial collateral ligament (MCL).
Transverse view comparisons of a painful left medial collateral ligament (MCL) and the right asymptomatic ligament. The left ligament is thickened with mixed echogenicity, which is representative of a partial tear. (nl, normal; pain, painful.)
Longitudinal view of the proximal lateral collateral ligament (LCL).
Nerves have a mixed hyperechoic and hypoechoic pattern that is attributed to the fascicles and their surrounding connective tissue. In the transverse plane, nerves have a distinguishable “honeycomb” pattern. In the longitudinal plane, they have a characteristic fascicular pattern. Nerves are mildly susceptible to anisotropy, but are not compressible. Blood flow is typically not visualized within nerves. Figures 39–24,Figures 39–25,Figures 39–26, and 39–27 show several examples.
Transverse view of the ulnar nerve seen in the ulnar groove.
Transverse view of the radial head where the supinator muscle, the posterior interosseus nerve (PIN), and the superficial radial nerve can be seen (SUP RAD).
Transverse view of the ulnar nerve as it passes through Guyon’s canal, which is composed of the pisiform and the hamate bone.
Transverse view of the median nerve (MN) as it passes through the carpal tunnel. (FDP, flexor digitorum profundus; FDS, flexor digitorum superficialis; FPL, flexor pollicis longus.)
L: Tendon and nerve sonography. Radiol Clin North Am 1999;37:691–711.
Muscles have a mixed echogenicity appearance. In the transverse plane, muscles have a “starry night” appearance. In the longitudinal plane, they exhibit a “feathery” appearance. Muscle is slightly compressible and is mildly susceptible to anisotropy. There is an absence of blood flow within muscles as visualized on ultrasound, although vasculature may be identified running with nervous tissue within fascial planes. Figure 39–28,Figure 39–29,Figure 39–30,Figure 39–31,Figure 39–32, and 39–33 show several commonly imaged muscles in contrasting views.
Transverse view of the quadriceps (QUAD) muscles. (RF, rectus femoris; VI, vastus intermedius; VL, vastus lateralis; VM, vastus medialis.)
Transverse view of the proximal rectus femoris (RF) and the vastus intermedius (VASTUS INT) with the femur seen deep to these muscles.
Anechoic area (***) representing a tear through the rectus femoris (RF). (VASTUS INT, vastus intermedius.)
Transverse view of the semimembranosus (SM) with an area of mixed echotexture, representing a partial tear.
Transverse view of the posterior medial knee with an anechoic cystic structure, marked with calipers, just lateral to the semimembranosus (SM), representing a Baker’s cyst.
Transverse view of the posterior medial knee. (MED GASTROC, medial gastrocnemius; SM, semimembranosus; ST, semitendinosus.)
F: Imaging nerve and muscle with ultrasound. Adv Clin Neurophysiol 2004;57:243–254.
In general, blood vessels are anechoic tubular structures that lack echotexture when visualized under ultrasound. Under Doppler examination, blood flow is readily visualized. Arteries and veins can be distinguished based on imaging features. Arteries are mildly compressible and are often seen pulsating under ultrasound examination. Veins are more readily compressible and typically have reduced flow compared with arteries. Examples of both can be seen in Figure 39–34.
Transverse view of the medial ankle. (A, artery; FDL, flexor digitorum longus; FHL, flexor halluces longus; MED MAL, medial malleolus; PT, posterior tibialis; TN, tibial nerve; V, vein.)
Bone is a well-defined, linear structure that is smooth in appearance and is typically hyperechoic compared with its surrounding structures. Because most of the ultrasound beam is reflected back to the transducer, structures deep to bone cannot be visualized. On the monitor this is depicted as an area devoid of shadows beyond the bony structure. This is referred to as acoustic shadowing. Figures 39–35,Figures 39–36,Figures 39–37,Figures 39–38,Figures 39–39,Figures 39–40, and 39–41 present several views.
Transverse view of the proximal patella.
Longitudinal view of the medial epicondyle with common origin of wrist flexor tendons.
View of the posterior glenohumeral joint using a 3–5 MHz curvilinear transducer. (HH, humeral head.)
Coronal view of the acromioclavicular (AC) joint, depicted with the joint capsule, clavicle, and acromion.
Longitudinal view of the anterior talofibular ligament (ATFL) as it attaches between the talus and the lateral malleolus (LAT MAL).
Longitudinal view of the proximal plantar fascia as it originates from the calcaneus (CALC).
Transverse view of the proximal plantar fascia as it originates from the calcaneus (CALC).