Overview of the Anterolateral Complex and the Anterolateral Ligament
In 2013, the New York Times and several other media outlets touted the discovery of a “new” knee ligament, the anterolateral ligament (ALL). In reality, the discovery was not new, but more of a “rediscovery” of a ligament of the knee that had been described in 1879 by a French Surgeon, Paul Segond. It has since been described in one form or another by numerous authors, notably Hughston, Terry, and others. The reason for its resurgence in popularity is for good cause – knee surgeons are continually working to improve the results of ACL surgery. It is generally agreed upon that the ligamentous structures (anterolateral complex) on that side of the knee may play a role in the rotational stability of the knee. It is important to recognize injuries to the antero lateral complex or ligament and know how to treat them appropriately.
Anatomy and Function of the Anterolateral Ligament – Anterolateral Complex
The anterolateral complex (ALC) contains several structures that start on the side of the knee and wrap around the front. There is some debate as to whether the anterolateral ligament of the knee (ALL) is a separately distinguishable ligament or whether it is a portion of the IT band or the knee capsule (anterolateral capsule). It is agreed that the ALL/ALC attaches near the lateral epicondyle of the femur and then at the anterolateral aspect of the tibia, just below the joint line. It is part of, or closely related to, the joint capsule, and it is located slightly in front of the lateral collateral ligament.
In conjunction with the anterior cruciate ligament (ACL), the ALL-ALC provides some degree of rotational stability to the knee. However, laboratory and biomechanical studies have shown that other structures, such as the IT band, the ACL, and the bony anatomy of the knee all play a role. In fact, the anterior cruciate ligament is the most important soft tissue structure for rotational knee stability. When the ACL is torn, it is possible that a torn ALL-ALC could cause even more knee laxity.
See illustration of the anatomy of the anterolateral ligament below. Visualized are important anatomic landmarks relevant to the anterolateral structures of the knee joint, such as the fibular head, Gerdy’s tubercle, the and the lateral epicondyle.
Do I Need an Anterolateral Ligament Reconstruction?
The answer to this question depends on many factors. Since the ACL is the most important ligamentous contributor to rotational knee stability, an anterior cruciate ligament injury must be addressed first. In fact, studies performed by Freddie Fu, MD and Volker Musahl, MD at the University of Pittsburgh have shown that a well performed, individualized, anatomic ACL reconstruction is the most important factor in restoring knee stability. If the ACL is left untreated, or the ACL surgery is done poorly, knee stability will not be restored.
Some patients may have excessive rotational knee laxity even after ACL reconstruction. There are some clinical tests, such as the pivot-shift test, that can help detect which patients large degrees of rotational knee instability. There are other more high-tech methods using iPad and accelerometer measurements that are able to more precisely measure knee stability. Other factors such as patient activity level, patient age, previous knee injuries, and the shape of the femur and tibia (bony morphology) that also must be considered.
Treatment of Anterolateral Ligament – Anterolateral Complex Injuries
While the exact number is being hotly debated, it is known that not all patients with ACL tears have anterolateral ligament complex injuries. The healing potential of the anterolateral ligament-complex is also not well understood. It is likely that many of these injuries can be treated with a brace in conjunction with an anatomic ACL reconstruction, and do not require a separate procedure. However, in some patients, an extra procedure will be needed to treat the anterolateral ligament-complex injury.
Many procedures have been described, but they all aim to accomplish a similar goal – to recreate the anatomy of the native anterolateral ligament-complex. All of the procedures involve using an extra tendon or similar structure (such as part of your own IT band, quadriceps tendon, or hamstrings tendon), and in some cases an allograft (tissue from a donor), and attaching it to the distal end of the femur and the proximal end of the tibia (the bones on each side of the knee). As previously mentioned, this is almost always done in combination with ACL reconstruction surgery. The postoperative course and rehabilitation protocol is usually not affected by the extra procedure.
How Do I Know if My Knee is Unstable or if there is an Injury to my Anterolateral Ligament-Complex?
Your surgeon will obtain plain x-rays of the knee. Although x-rays do not directly show soft tissue, they show the alignment of the bones. They can also show signs of an ACL injury, such as a Segond fracture (when the anterolateral ligament-complex pulls a piece of bone off the tibia instead of tearing directly). An MRI will also be needed, and will show if there is an injury to your ACL, meniscus, and cartilage. In some cases the MRI can detect damage to the anterolateral complex. Your surgeon will also perform a clinical examination, and tests such as the Lachman and Pivot-Shift will help gauge your knee stability. Some centers also utilize high-tech measurments of knee stability, such as video motion analysis software and inertial sensors.
The recent STABILITY trial demonstrated that a lateral extra-articular tenodesis (LET) procedure (modified Lemaire in this case) provided benefit to patients with ACL tears and high grade rotatory knee instability when undergoing an ACL reconstruction with a hamstring graft. Further studies including the STABILITY 2 Trial will work to elucidate which group of patients benefit most from an LET.
FAQ. Frequently Asked Questions about the Anterolateral Ligament
What is the ALL in the knee?
ALL stands for the anterolateral ligament. The ALL is really a complex of structures instead of a single ligament, and is often referred to as the anterolateral complex (ALC). The ALL plays a role in rotatory stability of the knee and can be injured along with the ACL.
What is the ALL ligament?
Near the fibular collateral ligament on the lateral side of the human knee is a ligament known as the anterolateral ligament (ALL). In his 1879 article, French surgeon Paul Segond described a ligamentous structure between the lateral femur and tibia, which is arguably the earliest description of the ALL. This ligament helps provide anterolateral rotatory stability to the knee, and can be injured in the setting of an ACL injury.
What is the function of anterolateral ligament?
The ALL or anterolateral complex has been shown to provide rotatory stability in conjunction with the ACL, and may play a role in preventing excessive rotatory motion of the tibia on the femur. Injury to the ALL may lead to instability of the knee and subsequent damage to other structures within the joint.
Where does anterolateral ligament attach?
The anterolateral ligament, or anterolateral complex, originates near the lateral epicondyle of the femur. It is described as being, on average, 9mm proximal and just posterior to the lateral epicondyle.
The ALL then connects at the anterolateral aspect of the tibia, just below the joint line, near between Gerdy’s tubercle ant eh fibular head. It is closely related to the joint capsule, and it is located slightly in front of the LCL.
Where is the anterolateral knee?
The anterolateral knee is the portion of the knee that is both toward the outside of the knee and the front part of the knee.
What is anterolateral ligament reconstruction?
Anterolateral ligament reconstruction is also known as lateral extra-articular tenodesis, or LET. This describes a variety of different techniques that are used to augment the anterolateral knee structures to help with rotatory instability in combination with anatomic ACL surgery.
Is ACL surgery a major surgery?
There are various types of ACL surgery, but the most common is known as ACL autograft surgery. This type of surgery involves taking a healthy tendon from another part of the patient’s body and using it to replace the damaged ACL. The donor tendon is usually taken from the patellar tendon, the quadriceps tendon, or the hamstring tendon. ACL surgery is considered to be a major surgery, although in most cases it is performed on an outpatient basis and the patient can go home the same day of the surgery.
Anterolateral Ligament-Complex References
- Burnham JM, Herbst E, Albers M, Pauyo T, Fu FH. (2016) The Anterolateral Complex of the Knee: A Comprehensive Review of Its Structure and Function. Journal of Clinical Orthopaedics, Dec. 2016. doi: 10.13107/jcorth.2454-5473.141.
- Herbst E, Albers M, Burnham JM, Shaikh HS, Naendrup J, Fu FH, Musahl V. (2017) The Anterolateral Complex of the Knee: A Pictorial Essay. Knee Surgery, Sports Traumatology, Arthroscopy, doi: 10.1007/s00167-017-4449-2. PMID: 28233023.
- Musahl V, Getgood A, Neyret P, Claes S, Burnham JM, Batailler C, Sonnerty-Cottet B, Williams A, Amis A, Zaffagnini S, Karlsson, J. (2017) Contributions of the Anterolateral Complex (ALC) and the Anterolateral Ligament (ALL) to Rotatory Knee Stability in the Setting of ACL Injury: A Roundtable Discussion. Knee Surgery, Sports Traumatology, Arthroscopy, April 2017. doi: 10.1007/s00167-017-4436-7.
- Herbst E, Burnham JM, Albers M, Musahl V, Fu FH. (2017) Layer-by-Layer Anatomy of the Anterolateral Complex of the Knee. Operative Techniques in Orthopaedics, doi: 10.1053/j.oto.2017.02.002.