O'Donoghue unhappy triad

O'Donoghue unhappy triad or terrible triad often occurs in contact sports, such as basketball, football, or rugby, when there is a lateral force applied to the knee while the foot is fixated on the ground. This produces the "pivot shift" mechanism.

The O'Donoghue unhappy triad comprises three types of soft tissue injury that frequently tend to occur simultaneously in knee injuries. 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)

The triad has subsequently been revisited considering the arthroscopic findings in patients with both ACL and MCL injuries, where lateral meniscal injury is more common than injury to the medial meniscus 2. Mechanistically this makes more sense during the pivot shift movement, as the lateral tibiofemoral compartment is compressed, causing failure of the lateral meniscus.

History and etymology

The unhappy triad is named after D H O'Donoghue, American orthopedic surgeon, who described it in 1950 4.

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Article information

rID: 1749
Section: Signs
Tag: knee, stub, refs
Synonyms or Alternate Spellings:
  • O'Donoghue triad
  • Unhappy triad
  • O'Donoghue's triad

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Cases and figures

  • MCL strain; bucke...
    Case 1: showing all three injuries
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  • Case 2
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  • Case 3
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    Case 4
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  • Case 5
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