A 25-year-old male athlete sustains a hyperextension injury to the knee. MRI shows a 'bone bruise' (marrow edema) in the posterolateral tibial plateau and the anterolateral femoral condyle, with an anterior cruciate ligament (ACL) tear. What specific mechanism and pivot shift injury pattern does this 'kissing contusion' pattern represent?
- A Direct valgus compression — medial compartment injury
- B Posterior cruciate ligament (PCL) injury — anterior tibial bone bruise
- C Anterior tibial translation with external tibial rotation (pivot shift mechanism) — classic ACL injury pattern ✓
- D Medial plateau fracture with MCL tear
Explanation
The 'kissing contusions' of the posterolateral tibial plateau and anterolateral femoral condyle form the bone bruise signature of an ACL injury via the pivot shift mechanism — anterior tibial subluxation with external rotation impacting the posterolateral tibial plateau against the anterolateral femoral condyle. This pattern is seen in 70–80% of acute complete ACL tears on MRI. Recognizing this bone bruise pattern confidently indicates ACL disruption even before the ligament itself is examined. PCL injuries produce anterior tibial bone bruises (dashboard injury). MCL injuries are associated with medial compartment bone bruises.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.