Every surgically reconstructed anterior cruciate ligament can retear. The risk ranges from one or two percent to more than 20 percent.
The replacement ligament (graft) chosen for your surgery can significantly increase or decrease your chance of a retear.
Using the MOON Knee Group risk calculators in this section, you can estimate your retear risk for different grafts. The calculators are based on data from more than 3,500 patients in a long-term ACL reconstruction study.
Calculate your expected failure based on the risk calculators and discuss with your doctor the advantages and disadvantages of each autograft type for you.
There is not enough data on using a quad tendon to include it in a calculator. Your doctor may still recommend this for you based on their experience and your injury and post-surgery goals.
The graft used in ACL reconstruction surgery is either an autograft or allograft.
Autografts are taken from your patellar tendon, hamstring or quad. You might hear this referred to as harvesting. This creates a second surgical location.
In allografts, the graft is taken from one of those locations on a cadaver.
Graft type or location does not change the functionality you can achieve with your reconstructed ACL. It does change your retear risk.
Allografts have three times the retear risk than autografts. If you are 22 or younger, the difference is significant.
The calculators use your height, weight, sex, sport and level of activity to predict your retear risk with different grafts. Your age, as you can read below, can have a critical impact on your retear risk for reconstruction using an allograft.
No identifying information from the forms is requested, collected or stored.
Injury can stretch your knee ligaments. This looseness (laxity) impacts your retear risk. You will need this information to interpret your retear risk. Your surgeon will determine in pre-surgery evaluation whether you have normal or high-grade laxity of your knee.
Retear risk should be your most important graft choice criteria.
When comparing graft types using the ACL retear risk calculators, use the absolute difference. That is, subtract the lower number from the higher number.
How much difference in retear risk is significant? When the absolute difference between retear risks is:
Many surgeons no longer use allografts (where the graft comes from a cadaver) in young patients. Why? Allografts are three times more likely to retear than autografts.
This difference is significant for those 22 and younger. Every competitive athlete younger than their mid-twenties should elect ACL reconstruction using autograft (with a replacement ligament from your body).
For those in their mid-twenties and older, the gap between the two methods becomes so small that it is insignificant. And those older than their mid-twenties suffer fewer ACL retears overall. Research so far provides no conclusive reason for this.
Regardless of graft method and source, you can reduce your risk of a repeat ACL tear by 40 to 60 percent.
How? By completing a MOON Knee evidence-based rehabilitation program coupled with return-to-sport training. (The MOON knee research program and rehabilitation guidelines are funded by federal grants, distributed at no cost and widely used.)
All ACL reconstruction surgery patients should fully complete their rehabilitation and training programs before resuming normal activity and especially when returning to a sport.