Musculoskeletal Ultrasound
Musculoskeletal Ultrasound tests whether you can obtain a diagnostic image of a tendon, ligament, nerve or muscle and then distinguish true structural failure from artifact. Dynamic assessment and contralateral comparison are central.
Core rules
- Tendons are echogenic and fibrillar with a compact, well-defined bundle; hold the probe perpendicular to the fibers.
- Anisotropy occurs when the beam is not perpendicular: the tendon becomes artificially hypoechoic and can mimic a tear. Heel-toe the probe to resolve it.
- Tendinopathy shows thickening, hypoechogenicity and loss of the normal fibrillar pattern without a discrete defect.
- A full-thickness tear shows a focal anechoic or hypoechoic gap with fluid, non-visualization of fibers, and cortical bone exposed; a partial tear shows a partial defect.
- Plantar fascia is abnormal above 4 mm at the calcaneal insertion.
- Median nerve cross-sectional area at the carpal tunnel inlet above 10 mm² suggests carpal tunnel syndrome.
Worked example
A supraspinatus tendon measures 8 mm, is hypoechoic, but the fibers remain continuous and the hypoechogenicity disappears when the probe is heel-toed perpendicular and confirmed in two planes. That is tendinopathy, not a tear. If instead there were a discrete fluid-filled gap with the tendon edges retracted and no fibers crossing on dynamic abduction, a full-thickness tear would be reported, with measurement of the retraction.
Traps that cost marks
Calling anisotropy a tear; overdiagnosing partial tears from a single plane; omitting dynamic testing; failing to compare with the asymptomatic side; and mistaking a calcification with shadowing for a tendon defect.