Findings
- Sagittal PDFS image of the knee joint at the level of lateral femoral condyle(1) shows impact contusions involving the posterolateral tibial plateau and lateral femoral condyle suggesting pivot shift mode of injury. This is a tell-tale sign of anterior cruciate ligament tear on radiography as well as MRI.
- Sagittal PDFS(2) and sagittal T2(3) images show marked fraying and hyperintense signal of the anterior cruciate ligament with defect in its superior half.
- With this mode of injury we also need to evaluate medial meniscus which in this case shows grade-I signal changes in the coronal PDFS image(4). The medial collateral ligament which is a commonly affected ligament is normal in this patient(5). Marked knee joint synovial effusion is noted(6) with debris suggestive of hemarthrosis.
Diagnosis
Pivot shift injury with impact contusions, anterior cruciate ligament tear, grade-I signal changes of medial meniscus and marked knee joint hemarthrosis.
Summary
Impact contusions of knee joint indicate the mode of injury and guide the evaluation of knee joint MRI. Similar impact contusions of medial pole of patella and lateral trochlear facet indicate transient patellar dislocation(link of our blog’s case in further reads section)
Further reads
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