In this X-ray, there is a tiny avulsion fracture where the anterolateral ligament has pulled off from the tibia.
What is the importance of an avulsion fracture?"
The presence of an avulsion fracture on X-ray indicates that there has been traction damage to soft tissues, usually from a ligament being pulled away from the bone - but the tiny bony fragment may be easily missed on X-ray.
Common avulsions include tibial tubercle avulsion and tibial spine avulsion. Avulsion of the anterolateral ligament is important not to miss.
Peer-reviewed papersQuote from peer-reviewed paper:
"....The Segond fracture is commonly regarded as pathognomonic for significant intra-articular pathology such as an anterior cruciate ligament (ACL) tear. There is worsened rotatory instability in patients with concomitant ACL tear and Segond fracture...."
Citation: Phua SKA, Lim JY, Li T, Ho SWL. The segond fracture: A narrative review of the anatomy, biomechanics and clinical implications. J Clin Orthop Trauma. 2023 Feb 13;38:102127. doi: 10.1016/j.jcot.2023.102127. PMID: 36860993; PMCID: PMC9969264.
Quote from peer-reviewed paper:
"Anterior cruciate ligament (ACL) avulsion fractures....result in significant disability if left untreated....[and] are caused by forceful hyperextension of the knee or by a direct blow over distal end of femur with the knee flexed."
Citation: Sundararajan SR, Rajasekaran S, Bernard SL. Displaced anterior cruciate ligament avulsion fractures: Arthroscopic staple fixation. Indian J Orthop. 2011 Jul;45(4):324-9. doi: 10.4103/0019-5413.82336. PMID: 21772625; PMCID: PMC3134017.
Quote from peer-reviewed paper:
"PCL [posterior cruciate ligament] avulsion fractures are rare injuries that can lead to significant morbidity when not recognized and treated properly"
Citation: Katsman A, Strauss EJ, Campbell KA, Alaia MJ. Posterior Cruciate Ligament Avulsion Fractures. Curr Rev Musculoskelet Med. 2018 Sep;11(3):503-509. doi: 10.1007/s12178-018-9491-2. PMID: 29869136; PMCID: PMC6105473..