What causes Lateral capsular sign in knee on radiograph?
Let me know in the comments.
Click to reveal the answer
Answer:
Small avulsion fragment from the lateral femoral condyle or lateral tibial plateau capsular insertion, seen on anteroposterior knee radiograph, representing severe lateral capsular ligament injury in anterior cruciate ligament (ACL) tear, often with associated Segond fracture.
Why is it called so?
Named for its location as a small fleck of bone adjacent to the lateral aspect of the lateral tibial plateau or femoral condyle, indicating avulsion from the lateral knee joint capsule — hence the term Lateral capsular sign.
Pathophysiology
High-energy rotational or valgus trauma causes forceful tension on the meniscotibial portion of the middle third of the lateral capsular ligament (or iliotibial band posterior fibers), resulting in avulsion of a bone fragment during ACL disruption from anteromedial tibial subluxation and pivot-shift mechanism.
Alternative names: Segond fracture (when referring to the tibial avulsion variant)
Other associated named signs: Segond fracture, lateral femoral notch sign
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
Improve Content And Help Your Colleagues!
Found an error in the post? Please let us know using our contact page and we will update it with due credits!
If you wish to contribute radiological images for this case (or any other article on the website), you can submit them here and you will be duly credited: Submit radiology case