Location of bone bruises and other osseous injuries associated with acute grade III isolated and combined posterolateral knee injuries.

BACKGROUND: Bone bruises on magnetic resonance imaging (MRI) are common in patients with acute knee ligament injuries and have been well described for injuries involving the anterior and posterior cruciate ligaments and the medial collateral ligament. These have not yet been described in detail for posterolateral corner injuries.

HYPOTHESIS: Acute grade III posterolateral corner (PLC) injuries are often accompanied by bone bruises located in the medial compartment.

STUDY DESIGN: Case series; Level of evidence, 4.

METHODS: One hundred two patients with acute grade III PLC knee injuries and MRI scans within 6 weeks of injury were prospectively identified. Images were reviewed for the location of bone bruises, which were defined as areas with high signal intensity adjacent to the joint surface on fat-suppressed, T2-weighted sequences.

RESULTS: Overall, 83 patients had at least 1 bone bruise and 56 patients had a bone bruise of the anteromedial femoral condyle. Tibial plateau fractures were found in 19 knees, with 12 in the anteromedial quadrant. Isolated PLC injuries were found in 28 patients; of this group, 18 had at least 1 bone bruise with 17 located in the anteromedial femoral condyle. Seventy-four patients sustained a combined ligamentous injury; 65 of these had at least 1 bone bruise on MRI and 39 had a bone bruise on the anteromedial femoral condyle. In patients with a combined injury to the PLC and anterior cruciate ligament (38), anteromedial femoral condyle bruises were seen in 19 patients and posteromedial tibial plateau bruises in 11.

CONCLUSION: Medial compartment bone bruises, most commonly of the anteromedial femoral condyle, were frequently found in patients with both acute isolated and combined PLC injuries. Thus, the presence of an anteromedial femoral condyle bone bruise should increase the level of suspicion of a concurrent PLC knee injury. In addition, we believe that the presence of a posteromedial tibial plateau bone bruise may be a secondary sign of a potential combined PLC injury in the setting of anterior cruciate ligament tear.