What's My Risk of Tearing My Uninjured ACL?

Tearing the anterior cruciate ligament (ACL) in one knee means you have an increased risk of tearing the ACL in your other knee. This is one of the findings from MOON Knee Group long-term ACL research.

No single cause accounts for the increased risk of a torn ACL in the opposite or contralateral knee, says Dr. Kurt Spindler, a knee specialist at Cleveland Clinic Sports Medicine and a leading participant in MOON Knee Group research.

“It could be your anatomy, your genetics or how aggressively you play. About 70 percent of ACL injuries happen without contact.”

What the Contralateral (Opposite) ACL Tear Risk Calculator Tells You

The calculator on this page estimates your risk of tearing the ACL in your uninjured knee within six years of having reconstruction surgery on the other knee. 

Like the autograft retear risk calculator, which estimates the risk of retearing a surgically reconstructed ACL, the contralateral ACL tear risk calculator is based on patient-reported outcomes from the more than 3,500 patients in MOON Knee Group’s research database.

How Can You Reduce Your Contralateral Tear Risk?

How can you reduce the chances of tearing your uninjured and your surgically reconstructed ACLs? Follow the guidelines on the Prevent ACL Injuries page. The recommendations are for preventing initial ACL tears as well as retears.

A Word About Terminology

  • Ipsilateral means on the same side of the body. For ACL injuries, it refers to the injured knee.
  • Contralateral means on the other side. For ACL injuries, it refers to the currently uninjured knee. 

You might hear the injured knee called the surgical or operative knee and the uninjured knee the nonsurgical or nonoperative knee. Knowing these terms can help you verify with the surgical team that your injured knee is the one clearly marked for surgery. 


Contralateral (Opposite) Knee ACL Injury Risk Calculator

The calculator requires entries in all fields.

Age (14-22)


Height / weight

Previous graft


Please indicate how often you performed each activity immediately before your injury.





Risk of tearing your non-injured ACL within 6 years:

This predicts the probability of tearing the ACL in your opposite (contralateral) uninjured knee within 6 years.

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