The X-ray above shows two of the most common plain films signs of ACL rupture
Avulsion of the lateral tibial plateau
Avulsion of the anterior tibial spine
The lateral tibial plateau avulsion, or Segond Fragment, is seen in greater than 75% of ACL tears. It has been shown to result from varus stress on the knee with internal rotation of the tibia, causing avulsion of bone at the insertion of the lateral joint capsule. Avulsion of the anterior tibial spine results from excessive tension on the ACL is usually accompanies rupture.
In acute knee trauma with pain and swelling, it is often difficult for emergency physicians to perform ligamentous examinations. These plain film hints can aid in the early diagnosis and prompt follow-up of ACL injuries.
References Stallenberg, B. Fracture of the posterior aspect of the lateral tibial plateau: radiographic sign of anterior cruciate ligament tear. Radiology. 1993 Jun; 187(3): 821-5.
Wheeless, C. “Evaluation of the ACL tear.” Wheeless’ Textbook of Orthopaedics N.p., 30 Nov. 2008 Web. 17 Apr. 2010.
This "EM Lightbox" case was authored by guest blogger, Dr. Eric Silman.