Knee x-ray shows an avulsion fracture (arrow) of the inferio | Figure 1

CincyKidsRad

Cincinnati Children's Radiology

Knee x-ray shows an avulsion fracture (arrow) of the inferior pole of the patella and a large knee effusion. This type of avulsion fracture, called a patellar sleeve avulsion, is unique to children and occurs with forceful contraction of the quadriceps muscle against resistance. #MSKMonday

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AP and lateral radiographs of the knee show a small avulsion fragment along the lateral aspect of the tibial epiphysis and a large knee effusion. This type of fracture represents an avulsion of the lateral collateral ligament and is known as a Segond fracture. It is important to recognize as it is almost always associated with an ACL injury. #MSKMonday](https://app.figure1.com/case-detail/55c9b20c-bfdd-46ec-8d3d-6babdb91ef7c)

Lateral radiograph of the knee (image 1) shows an avulsion fracture (arrow) of the posterior aspect of the tibia epiphysis and a large knee effusion (arrowhead). Sagittal CT image (image 2) shows the avulsion fragment (arrow). Sagittal T2 weighted MRI (image 3) highlights the avulsion fragment (arrow) and the large hemarthrosis (arrowhead). The proton density MRI (image 4) highlights that the avulsion fracture is connected to the posterior cruciate ligament (arrow). Posterior cruciate ligament avulsion fractures are uncommon. They typically occur after motor vehicle collision. However it can also occur as a jumping injury where the individual lands on a plantarflexed foot with the knee in flexion.

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