Skeletal radiology
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The "arcuate sign" is considered a pathognomonic sign for injuries of the posterolateral (PL) corner of the knee. The purpose of our study was to identify different patterns of injury to the fibular head that may associate with injuries to specific ligaments and tendons of the PL corner of the knee. The anatomic relations between the insertions of fibular collateral ligament (FCL), biceps femoris tendon (BFT), popliteofibular ligament (PFL), and arcuate ligament in normal cadaveric knees were also investigated. ⋯ The PFL and arcuate ligament were seen to attach directly to the posterior and medial aspect of the styloid process of the fibular head. The FCL and BFT attached as a conjoined structure on the lateral aspect of the fibular head lateral, anterior and inferior to the attachment site of the PFL and arcuate ligament. Injury to the arcuate ligament or PFL was diagnosed in 8 patients who presented with a small avulsion fracture of the styloid process of the fibula (n=2), bone marrow edema in the medial aspect of the fibular head (n=3), or both (n=3). In 4 patients with injury to the conjoined tendon or FCL, a larger avulsion fragment and more diffuse proximal fibular edema were seen. Radiographic and MR imaging findings in injuries of the posterolateral corner of the knee may suggest injury to specific structures inserting in the fibular head.