The MOON Knee ACL Autograft Retear Risk Calculator

If you’ve had or will have ACL reconstruction surgery using an autograft, you can estimate your noncontact retear risk using the Autograft Retear Risk Calculator below.

An autograft is when your ACL is reconstructed using a tendon from your body. Replacement tendons for autografts are taken from the patellar tendon, hamstring or quadriceps. Graft source location is a factor in retear risk.

All Autografts Have Lower Retear Risk than Allografts

In an allograft, the replacement tendon comes from a cadaver. Allografts have a three times higher risk of retear than autografts. The difference in risk is especially significant for young athletes. Many surgeons no longer use allografts for younger athletes.

Pre-Surgery Knee Laxity Matters

How loose your knee is after injury is called laxity. The higher the degree of laxity, the more the research recommends using your patellar tendon for autograft surgery.

Knee laxity can only be determined by a skilled professional doing a physical examination.

What If You’re Older Than 22?

The difference in retear risk from graft choice is most significant for those 22 and younger. For those in their mid-twenties and older, the difference in retear risk from graft choice becomes smaller the older you are. And those older than their mid-twenties suffer fewer ACL retears overall.

Bottom line: the data says that if you’re older than your mid-twenties, you can choose—in consultation with your surgeon—the graft type that works best for you.


Talk to Your Doctor

The Autograft Retear Risk Calculator is based on MOON Knee Group follow-up research six years after surgery. 

You can use your estimated failure risk in shared decision-making with your medical provider. Note that based on a variety of factors, the recommendation for your surgery can vary from your estimated risk.


ACL Autograft Retear Risk Calculator

To estimate your risk of retearing your surgically reconstructed ACL by autograft, enter your age, weight, height, sex, sport and activity level. This calculator is valid for ages from 14 to 22  and only includes results for ACL autograft using patellar tendon or hamstring. While reconstruction using a quadriceps tendon is growing in use, there is insufficient long-term research to include it in the calculator.

Age (14-22)


Height and weight


Please indicate how often you performed each activity in your healthiest and most active state during the last 12 months.





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