O'Donoghue's unhappy triad

Case contributed by The Radswiki
Diagnosis certain


Twisting injury of the knee.

Note: This case has been tagged as "legacy" as it no longer meets image preparation and/or other case publication guidelines.


MR images demonstrate O'Donoghue's unhappy triad.

  • wavy anterior cruciate ligament with interrupted proximal attachment, reflecting complete tear
  • grade III tear of medial collateral ligament, with surrounding soft tissue edema
  • horizontal tear of the posterior horn of medial meniscus reaching the inferior articular surface

Mild knee effusion.

Bone marrow edema of the lateral tibial plateau and lateral femoral condyle.

Case Discussion

O'Donoghue described the injuries as:

  1. anterior cruciate ligament (ACL) tear
  2. medial collateral ligament (MCL) tear / sprain
  3. medial meniscal tear (lateral compartment bone bruise)

These images are from Dr. John Hunter's amazing MSK collection. Dr. John Hunter is a professor in the department of radiology (musculoskeletal section) at UC Davis School of Medicine.

This case was donated to Radiopaedia.org by Radswiki.net.

How to use cases

You can use Radiopaedia cases in a variety of ways to help you learn and teach.

Creating your own cases is easy.

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.