Proximal Hamstring Tendon Avulsion on Ultrasound
Ultrasound Semiology of Complete Avulsion
In complete avulsion of proximal hamstring tendons, longitudinal scanning (including extended field of view) demonstrates absence of proximal hamstring tendons in the region of the ischial tuberosity (ischium) with distal retraction of the tendon stump. An avulsion fracture fragment may be identified. The ischial tuberosity (I, ischium) serves as an anatomical landmark.
Partial Injury and Hematoma
In partial semimembranosus injury, short-axis and long-axis views demonstrate partial muscle tear with hematoma and increased posterior through transmission. The semitendinosus (ST) and biceps femoris (BF) are identified as adjacent structures. Chronic semimembranosus tear is described separately.
Scanning Planes
| Plane | Assessment Criteria |
|---|---|
| Short axis | Partial muscle tear, hematoma |
| Long axis | Tendon integrity, retraction, fracture fragment |
| Extended field of view | Complete avulsion, measurement of distal stump retraction |
Anisotropy Artifact in Tendon Assessment
Hamstring tendons are susceptible to anisotropy artifact: with non-perpendicular beam incidence, the structure appears hypoechoic, mimicking pathology. To overcome this, tilt the transducer (heel-toe manoeuvre / angulation)—a small tilt (5–15°) restores perpendicular incidence and normal echogenicity. If the finding disappears with tilting, it is an artifact rather than a tear.
Anatomical Landmarks [to be clarified]
Detailed threshold values for retraction distance and criteria for differentiating acute versus chronic injury are not provided in the available fragments [to be clarified].
Frequently asked questions
How does complete avulsion appear on ultrasound?
Absence of proximal hamstring tendons with distal retraction of the tendon stump; an avulsion fracture fragment may be present. Landmark: ischial tuberosity (ischium).
What are the findings of partial semimembranosus tear?
Partial muscle tear with hematoma and increased posterior acoustic enhancement on short-axis and long-axis views.
How do you differentiate artifact from true tendon tear?
Tilt the transducer (heel-toe / angulation, 5–15°). If the hypoechoic area disappears with tilting, it is anisotropy rather than pathology.
Which approach is best for assessing retraction?
Longitudinal (long axis) with extended field of view—allows assessment of tendon absence and distal retraction.