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 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 anterolateral complex or ligament and know how to treat them appropriately.

sports medicine sports injury pivot shift pain knee doctor IT band injury anterolateral ligament anterolateral complex all alc acl
Visual layout of the various structures described of the anterolateral knee, as studied and reported by Freddie Fu, Volker Musahl, Elmar Herbst, and Marcio Albers (KSSTA 2017). BLACK = anterolateral Ligament (ALL), RED = capsulo-osseous layer of the IT band, BLUE = mid-third capsular ligament, LCL = lateral collateral ligament, LE = lateral epicondyle, GT = Gerdy’s tubercle. © OrthoConsult

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 (ALL) is a separately distinguishable ligament or whether it is a portion of the IT band or the knee 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.

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.

sports medicine sports injury pivot shift pain knee doctor IT band injury anterolateral ligament anterolateral complex all alc acl
The Lemaire (A) and Marcacci (B) techniques for lateral extra-articular tenodesis. Image from Slette EL, Mikula JD, Schon JM, Marchetti DC, Kheir MM, Turnbull TL, LaPrade RF. Biomechanical Results of Lateral Extra-articular Tenodesis Procedures of the Knee: A Systematic Review. Arthroscopy. 2016 Dec;32(12):2592-2611. doi: 10.1016/j.arthro.2016.04.028. Review. PubMed PMID: 27324970.

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.

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.

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