The hand is the most commonly injured part of the body. Hand and wrist disorders can be accurately assessed with high-frequency transducers.

Ultrasound is an excellent imaging modality as it is relatively safe, inexpensive and portable. Ultrasound imaging can be used to study the movement of anatomical structures such as tendons. The investigation is non-invasive and free of the harmful effects of ionising radiation.

The patient’s finger is covered with a gel and then a small ultrasound probe is passed over the finger. The operator then passively moves the finger and observes tendon movement on the screen.

NORMAL ANATOMY

Normal tendon is moderately hyperechoic when compared to skeletal muscle.

The tendon fibrils are represented by a pattern of parallel internal echoes.

There are 2 flexor tendons of the fingers:

• Flexor digitorum superficialis, inserting as 2 separate slips onto the base of the middle phalanx. Fig. 1
• Flexor digitorum profundus, inserting onto the distal phalanx. Fig. 2

In transverse section, the bundles of fibres give rise to a finely punctate echogenic pattern. Fig. 3

Extensor digitorum tendons 

Unlike the flexors, there is only an extensor digitorum, inserting onto the distal phalanx. Fig. 4 The tendon is extremely thin and lies intimately against the bone.

Pulleys

The flexor tendons are secured in place by a series of pulleys which are fibrous bands wrapping over the tendons and attaching to the bone.

• Annular pulleys: which wrap transversely over the tendons. Fig. 5
• Cruciate pulleys: which are paired and cross diagonally over the tendons.

The synovial sheath is depicted as a thin echogenic fluid-containing structure that surrounds the echogenic tendon fibers. The synovial fluid is usually but not always anechoic. A small amount of fluid is frequently seen within the extensor tendon sheaths of the wrist or hand in individuals with normal anatomy. Fig. 6

At sonography, ligaments should appear as echogenic fibrillar structures. Fig. 7