Semimembranosus distal tendon avulsion

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Semimembranosus distal tendon avulsion is a specific type of hamstring avulsion injury that can occur in the knee.

Pathology

External rotation and abduction of the flexed knee or valgus force applied to the tibia. Associated injuries include anterior cruciate ligament (ACL) rupture, posterior horn medial meniscal tear and posteromedial corner injuries.

Radiographic features

Plain radiograph

Very hard to detect on plain film and may be seen on lateral view as a displaced bony fragment.

MRI

MRI is the best modality to detect the lesion and additional associated soft tissue injuries. The small bony fragment may be displaced or in situ. Associated anterior cruciate ligament rupture, posterior horn of medial meniscal tear and meniscocapsular separation are usually present.

Differential diagnosis

  • fat in the distal semimembranosus tendon
    • recognized normal variant
    • the tendon attachment to the tibia should remain intact
    • no tendon retraction