Does Your New ACL Need a "Backup"? Understanding Lateral Extra-Articular Tenodesis (LET)
If you are preparing for Anterior Cruciate Ligament (ACL) reconstruction, you might have heard me or another surgeon mention an "add-on" procedure called a Lateral Extra-Articular Tenodesis (LET).
It sounds complicated, but the concept is actually quite simple. It’s essentially a "backup" reinforcement for your new ACL.
We recently reviewed the latest medical research—including the landmark STABILITY 1 study—to help you understand what this procedure is, why it is used, and whether it might be right for you.
What is LET?
Standard ACL surgery focuses on fixing the ligament inside your knee joint. However, there are ligaments on the outside (lateral side) of the knee that also help keep your knee stable, specifically when you twist or pivot.
An LET procedure involves using a strip of tendon (usually from the side of your knee/IT band) to create a restraint on the outer side of the joint.
Think of the ACL as the main seatbelt for your knee. The LET is like adding a second seatbelt or a "deadbolt" lock—it provides an extra layer of security to stop the knee from rotating too much.
The Evidence: The STABILITY 1 Study
One of the most important pieces of research guiding our decisions today is the STABILITY 1 Study [1]. This was a massive, high-quality clinical trial that followed over 600 young, active patients.
The results were clear:
Reduced Failure Rates: The study found that adding the LET procedure to a standard hamstring ACL reconstruction significantly reduced the risk of the graft failing.
Clinical Success: Patients who had the "backup" LET procedure had a re-tear/failure rate of only 4%, compared to 11% in the group that only had the ACL fixed. That is a massive reduction in risk for high-level athletes.
Why Surgeons Do It
Based on the STABILITY 1 trial and recent reviews of the literature, we know that adding an LET offers:
Drastically Lower Re-Tear Risk: As seen in the STABILITY data, the risk of graft rupture is significantly lower in high-risk groups.
Better Stability: Patients often have less "pivot shift" (that unstable feeling where the knee wants to give way).
Protecting the Graft: Laboratory studies show that the LET takes pressure off the new ACL graft, protecting it while it heals [6].
The Trade-off: Why Not Do It for Everyone?
If it protects the ACL, why don't we do this for every patient? The research highlights a few reasons why we are selective:
"Over-tightening" the Knee: There is a risk of "overconstraining" the knee. If the outer side is too tight, it can change how the joint surfaces rub together [6].
Long-Term Considerations: Some long-term data (19-year follow-up) suggests a potential for slightly higher rates of wear and tear (osteoarthritis) in the outer part of the knee decades later.
The Verdict: Who Needs It?
The current consensus is that LET is a "game-changer" for those at high risk. You and your surgeon might consider this procedure if:
You are young (under 25) and active in pivoting sports like soccer, football, or basketball.
You have "high-grade" looseness: If your physical exam shows a lot of rotational instability (a positive pivot shift test).
This is a revision surgery: If you have already torn your ACL once.
You have hyper-laxity: If you are naturally very flexible.
Summary
Adding an LET is a powerful tool. As the STABILITY 1 study showed, it trades a small potential risk of stiffness or future wear for a massive reduction in the risk of tearing your ACL again in the short term.
References:
Getgood AM, et al. Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial. The American Journal of Sports Medicine, 2020.
Ni QK, et al. Lateral Extra-articular Tenodesis Notably Reduced Residual Knee Instability... Orthopaedic Journal of Sports Medicine, 2025.
Gibbs CM, et al. Anterior cruciate ligament reconstruction with lateral extraarticular tenodesis better restores native knee kinematics... Knee Surgery, Sports Traumatology, Arthroscopy, 2022.
Risvas K, et al. Can lateral tenodesis improve the rotational stability of the ACL reconstruction? A finite element analysis. PLoS One, 2024.
Castoldi M, et al. A Randomized Controlled Trial of Bone-Patellar Tendon-Bone Anterior Cruciate Ligament Reconstruction With and Without Lateral Extra-articular Tenodesis: 19-Year Clinical and Radiological Follow-up. The American Journal of Sports Medicine, 2020.
Giusti S, et al. Does Adding LEAP to ACL Reconstruction Reduce Graft Failure? A Systematic Review and Meta-Analysis... Journal of Clinical Medicine, 2025.
