What Is the ALL? Understanding the Forgotten Knee Ligament

When it comes to knee injuries, most people have heard of the ACL, MCL, and meniscus. But there’s another key player in knee stability that often flies under the radar—the anterolateral ligament, or ALL.

While lesser known, the ALL plays a significant role in rotational stability of the knee, especially in athletes and active individuals. And in recent years, orthopedic surgeons have started paying closer attention to this ligament—particularly when treating ACL injuries that just don’t seem to heal quite right.

What Is the Anterolateral Ligament (ALL)?

The anterolateral ligament is a thin band of tissue located on the outside of the knee. It runs from the thigh bone (femur) to the shinbone (tibia), near the lateral meniscus. Its job? Helping to control rotation of the knee, especially during twisting or pivoting movements.

Although researchers had speculated about its existence for more than a century, the ALL wasn’t clearly identified and named until 2013. Since then, it’s been the focus of growing interest in sports medicine and orthopedic surgery.

How Does the ALL Work With the ACL?

The ALL and ACL work together to keep the knee stable—especially during fast changes in direction, cutting movements, or twisting motions. When the ACL is torn, the ALL often tears too, though it can be difficult to detect on traditional imaging.

This is why some patients who undergo ACL reconstruction continue to experience a “pivot shift”—a sensation of instability or “giving out” when rotating the knee. In many of these cases, an untreated ALL injury may be to blame.

How Do ALL Injuries Happen?

ALL injuries usually happen alongside ACL injuries. In fact, studies show that the ALL is torn in up to 90% of ACL ruptures. The typical mechanism is a non-contact twisting injury—like pivoting suddenly during sports or landing awkwardly from a jump.

Symptoms of an ALL tear may include:

Ongoing instability or giving way, even after ACL reconstruction
Difficulty with pivoting or cutting movements
Residual knee pain on the outer side
A sensation that the knee isn’t “trustworthy,” especially during athletic activity

Diagnosing an ALL Tear

Diagnosing an ALL tear can be challenging. It’s a small, delicate structure that may not show up clearly on MRI scans, particularly if there’s swelling or associated damage to the ACL or meniscus. Some ALL tears are only discovered during ACL surgery, when the surgeon gets a close-up look at the knee structures.

Orthopedic specialists may use a combination of:

Physical exams to assess rotational instability
MRI imaging (preferably with a 3T scanner for better resolution)
Surgical findings during ACL reconstruction or revision surgery

Treatment: Why Surgeons Are Reconstructing the ALL

In many cases, ACL surgery alone is enough to restore stability to the knee. But when instability persists—or in athletes at high risk of re-injury—surgeons may opt to reconstruct the ALL as well.

ALL reconstruction is a minimally invasive procedure, often done at the same time as ACL reconstruction. It uses a tendon graft (often a portion of the iliotibial band or hamstring tendon) to reinforce the torn ligament and restore rotational stability.

Recent studies show that adding ALL reconstruction to ACL surgery can reduce the risk of re-tear and improve knee stability—especially in young athletes or those with high-demand sports goals.

Final Thoughts: Don’t Overlook the ALL

If you've had an ACL injury or reconstruction and your knee still doesn’t feel quite right, the anterolateral ligament might be the missing piece. With increasing research and attention on this forgotten ligament, orthopedic care is becoming more comprehensive and precise.

Your knees deserve expert care.If you’re struggling with instability, knee pain, or a failed ACL repair, it’s time to talk to a specialist who understands the full anatomy of the knee—including the ALL.

📞 Schedule a consultation today to get clarity—and confidence—in every step you take.