What is a Lateral Extra-articular Tenodesis (LET)?

An LET is a small extra procedure on the outside of your knee. It is done at the same time as ACL reconstruction. Its job is to reduce the rotational wobble that can lead to your new ACL graft tearing again.

The problem LET solves

When you tear your ACL, you lose the ligament that stops your shin bone from sliding forward and rotating under your thigh bone. ACL reconstruction fixes most of that — but some knees still have a tendency to "shift" when you twist or cut.

This twisting motion is called rotational instability. Surgeons test for it with a manoeuvre called a pivot shift test. A strong "catch and shift" feeling (grade 2 or 3) means your knee has significant rotational laxity. That puts extra stress on your new ACL graft every time you pivot — and increases the chance it will re-tear.

The LET is designed to control that rotation.

What exactly is the LET procedure?

LET stands for Lateral Extra-articular Tenodesis.

• Lateral — it is on the outside (lateral side) of the knee.
• Extra-articular — it is outside the joint capsule. The surgeon never opens the joint itself for the LET part.
• Tenodesis — a strip of tendon is anchored (fixed) to bone to act as a check-rein.

The surgeon takes a thin strip of tissue from the bottom of the iliotibial band (IT band), the thick band that runs down the outside of your thigh. They leave one end attached to its natural insertion point on the shin bone (a bump called Gerdy's tubercle). The other end is passed under the fibular collateral ligament and fixed to the outside of the thigh bone with a staple or screw.

This strip acts like a tether. It limits how far the shin bone can rotate inward, reducing the stress on the ACL graft inside the joint.

What does the evidence show?

The best evidence comes from a large randomized controlled trial called STABILITY 1, published in 2020.^[1] It enrolled 618 young patients (ages 14–25) undergoing ACL reconstruction with hamstring autografts. Half got ACL reconstruction alone. Half got ACL reconstruction plus an LET.

At 2 years, the results were clear:

• Graft rupture: 11% in the ACL-only group vs. 4% in the ACL + LET group — a roughly two-thirds reduction in re-tear risk.^[1]
• Composite failure (graft rupture or persistent knee shifting): 40% vs. 25%.^[1]
• Functional scores and return-to-sport rates were similar between the two groups.^[11]

Multiple systematic reviews and meta-analyses of randomized trials confirm: adding a lateral procedure to ACL reconstruction reduces graft failure by approximately 60–70% and significantly improves pivot-shift outcomes compared to ACL reconstruction alone.^[5][6][7][8]

Importantly, a companion safety paper found no increase in serious complications.^[4] Hardware irritation requiring a small removal procedure was slightly more common in the LET group, and one 2026 study found a 2-fold increase in knee stiffness (arthrofibrosis) in adolescents after the combined procedure.^[32] Your surgeon will weigh these trade-offs carefully.

Who is most likely to benefit?

The evidence is strongest for a specific group of patients. You are more likely to benefit from adding an LET if you have two or more of these features:^[1][2]

• Age under 25 — younger patients have a higher baseline risk of graft failure.
• Returning to pivoting or cutting sports — soccer, basketball, football, skiing, gymnastics, and similar activities.
• High-grade pivot shift (grade 2 or 3) — your knee has a strong "catch and shift" when your surgeon tests it.
• Very flexible joints ("double-jointed") — a Beighton score of 4 or more, or your knee bends backward past straight by more than 10°.
• Hamstring autograft — the highest-risk graft configuration in young pivoting athletes.
• Revision surgery — this is your second or third ACL surgery on the same knee.
• Backward-tilting shin bone — a posterior tibial slope of 12° or more, which puts more force on the ACL graft.^[2]

LET is not for everyone. For a lower-risk patient — say, someone over 40 returning to recreational activity — the extra procedure may not add enough benefit to justify it. This is always your surgeon's decision, based on your full picture.

LET and the anterolateral ligament (ALL) — what is the difference?

You may have heard about a procedure called ALLR (anterolateral ligament reconstruction). The ALL is a small ligament on the outside of the knee that was described anatomically more recently.

LET and ALLR are closely related. Both are lateral extra-articular procedures — both work on the outside of the knee to control rotation. The main difference is technique: LET uses a strip of the IT band woven under the fibular collateral ligament, while ALLR reconstructs the ALL directly, often using a separate graft.

Studies comparing LET and ALLR directly show similar results for re-tear rates and function.^[5][9] Many surgeons use the terms almost interchangeably in patient discussions, though they are technically different operations. The SANTI Study Group — one of the world's leading research groups on this topic — uses ALLR and has published large prospective cohort data showing a 4% graft failure rate with ACLR + ALLR versus 11% with hamstring ACLR alone.^[3]

The bottom line: whether your surgeon prefers LET or ALLR, both aim to give your ACL graft a better chance of surviving the demands you put on your knee.