O'Donoghue's unhappy triad
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There is a horizontal cleavage type tear in the medial meniscus. ACL contour is disrupted with a change in the orientation, representing ACL complete tear.
There is mild fluid accumulation around the MCL representing MCL injury.
There is moderte joint effusion.
Note the characteristic bone marrow contusion in the posterolateral tibial plateu and lateral femoral condyle. If the impaction in the lateral femoral sulcus exceeded 2mm, it would represent femoral notch sign which is highly suggestive of ACL injury.
O'donoghue's unhappy triad consists of medial meniscal tear, ACL tear and MCL injury. It usually happens in the pivot shift injuries. Today we believe that lateral meniscal tear actually happens more than medial meniscal tear in this type of injury.
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- Pao DG. The lateral femoral notch sign. Radiology. 2001;219 (3): 800-1. Radiology (full text) - Pubmed citation
- Remer EM, Fitzgerald SW, Friedman H et-al. Anterior cruciate ligament injury: MR imaging diagnosis and patterns of injury. Radiographics. 1992;12 (5): 901-15. Radiographics (abstract) - Pubmed citation