Core curriculum case illustration: [Stieda fracture (avulsion fracture of the medial femoral condyle)].

This is the 30th installment of a series that will highlight one case per publication issue from the bank of cases available online as part of the American Society of Emergency Radiology (ASER) educational resources. Our goal is to generate more interest in and use of our online materials. To view more cases online please visit the ASER Core Curriculum and Recommendations for Study online at: http://www.erad.org/page/CCIP_TOC . A Stieda fracture is an avulsion injury from the medial femoral condyle of the origin of the medial collateral ligament. The medial collateral ligament originates superiorly from the medial femoral condyle and has superficial and deep fibers. On radiographs, the avulsion fracture at or near the medial femoral condyle near the attachment site of the medial collateral ligament is usually characteristic. Isolated partial or complete MCL injuries can be treated nonoperatively with good outcomes. Reconstruction of the medial ligamentous structures of the knee is usually performed if there is persistent valgus laxity or anteromedial rotatory instability after nonoperative management.