August 18, 2016
11 min read

Focus on anterolateral knee structures sparks debate, fosters more research

Results from this debate, such as new findings, may substantially alter the way ACL-deficient knees are treated in the future.

You've successfully added to your alerts. You will receive an email when new content is published.

Click Here to Manage Email Alerts

We were unable to process your request. Please try again later. If you continue to have this issue please contact

International orthopaedic knee surgeons and researchers are taking a closer, more critical look at the anterolateral soft tissues of the knee and the role the extra-articular knee structures play in the success of ACL reconstructions, which has led to a wide-scale, heated debate. They are focused on one anterolateral extra-articular knee structure in particular because some surgeons doubt the structure even exists, while others have identified it and call it the anterolateral ligament or ALL.

“We are dealing with one of the most popular orthopaedic procedures, the ACL reconstruction, which the ALL is related to. This explains the great interest among the orthopaedic community in an issue that could result in a substantial change in the approach to the ACL-injured knee,” Andrea Ferretti, MD, of S. Andrea University Hospital in Rome, told Orthopaedics Today Europe. “This so-called heated discussion could be explained by the lack of convincing MRI or arthroscopic findings able to clearly show its existence. Moreover, the need for an open approach to treat a ligament with this pathology, in an era of minimally invasive techniques, is far from being accepted.”

Pros and cons

Andrea Ferretti, MD
Andrea Ferretti

The believers define the ALL as a structure that may tear in conjunction with ACL tears or during extreme tibial rotation that occurs in high-level athletes who ski or play soccer, for instance. ALL proponents also say it possibly plays a role in somewhat rare Segond fractures, a small tibial plateau bone chip identified in the late 1800s by French surgeon Paul Ferdinand Segond, that may occur in high-energy rotatory knee injuries.

Non-believers in the ALL contend it is most likely the iliotibial (IT) band, or a deep layer of the IT band, that is affected in these situations, along with other structures in what they call the anterolateral complex. The opponents to the ALL concept say those are the areas that must be addressed in conjunction with these knee injuries, especially when the ACL is torn.

Orthopaedics Today Europe spoke with international experts on both sides of the debate concerning the ALL based on their research and clinical experience related to anterolateral knee injuries, the ALL and ACL tears.

Debate at ESSKA Congress

Steven Claes, MD, PhD
Steven Claes

Steven Claes, MD, PhD, of Belgium, and Freddie H. Fu, MD, DSc(Hon), DPs(Hon), of Pittsburgh, USA, debated each other at the European Society of Sports Traumatology, Knee Surgery and Arthroscopy (ESSKA) Congress, before a standing-room only crowd, on whether the existence of the ALL is fact or fiction.

Claes, who contends the ALL exists and whose anatomical research with colleagues on embalmed cadavers in support of that claim was published in the Journal of Anatomy, said in his concluding statement during the debate, “I think it is better to join forces in this field for the best of our patients.”

Fu, based on his dissections, clinical experience and review of the literature, noted the anterolateral complex, which is formed by the IT band and it connections to the femur as described by Kaplan, the deep capsule-osseous layer, as well as the anterolateral capsule, synergistically limit knee internal rotation. Of all these structures, the IT band plays the most important role.

Coronal MRI image of a left knee with an acute ACL injury
Coronal MRI image of a left knee with an acute ACL injury, which directly depicts a Segond fracture (red arrow) as a bony avulsion of the anterolateral ligament or ALL (blue arrows).

Image: Claes S

“The key is to do an accurate layer-by-layer dissection. Anatomy is persistent,” Fu told Orthopaedics Today Europe, “whereas dissection is variable as represented by the conflicting anatomical descriptions of the ALL. As the late anatomist Pau Golanó, MD, often said, we should look at nature, but not create nature.”

Supporting the reconstructed ACL

Regardless of the upshot of this controversy, many surgeons and researchers seem to hope it ultimately helps patients with ACL tears regain knee stability and function, safely return to play and avoid knee osteoarthritis (OA) in later years.

In support of his position, Claes said during the debate, “I would say that by now, it is scientifically proven the ALL not only exists, but the injuries can be diagnosed and seen on MRI and ultrasound.”

He mentioned the work of several investigators during his presentation that supports the existence of the ALL, including that of Bertrand Sonnery-Cottet, MD.

“It acts as a rotatory restraint and thus affects the pivot shift [PS]. It explains the Segond fracture, which has been proven, as well, and a combined ACL plus ALL reconstruction indeed does work. I must admit, though, there is still plenty of work to be done,” Claes said.


To highlight the different structures on the lateral side of the knee, Fu said during the debate, “I would propose we call this whole structure the anterolateral complex. I think we can talk and then we can improve the whole knowledge and move forward.”

Persistent pivot shift

Importantly, the debate at the ESSKA Congress was not fabricated as are some debates at scientific orthopaedic meetings. In interviews after the meeting, Claes and Fu reiterated their respective cases for and against the existence of the ALL. Claes told Orthopaedics Today Europe he started studying this area when his patients who underwent perfectly executed, anatomical ACL reconstructions had a substantial PS — excessive anterior translation and internal rotator instability — that persisted.

“Simplified, one could say the ACL attests for this excessive anterior translation while the ALL deficiency then leads to this internal rotatory instability with both phenomenon present in the positive PS test,” he said.

“The ALL story can explain a few of these cases,” Claes said, noting the orthopaedic community must look beyond the ACL when treating ACL-injured patients and athletes, in particular, who pivot from their knees using extreme amounts of energy and require a perfectly stable knee.

Extra-articular treatment may be needed

Freddie H. Fu, MD, DSc(Hon), DPs(Hon)
Freddie H. Fu

Fu, who has studied knee ligaments and extra-articular knee structures for about 40 years, told Orthopaedics Today Europe that sometimes during ACL surgery other extra-articular work is indicated.

The ACL, PCL, medial collateral ligament and lateral collateral ligament are well-defined, he noted.

 anatomic dissection denote the structures of the lateral side of the left knee
This anatomic dissection denote the structures of the lateral side of the left knee. After removal of the superficial layer of the iliotibial band (ITB), the anterolateral capsule and Gerdy’s tubercle (GT) are shown. The part of the ITB from the Kaplan fibers to its connection to the GT form a functional arc, which restrains internal tibial rotation.

Images: Fu F

“We cannot imagine a ligament that we are not sure is there. It is almost silly even to imagine something that is so important, people do not even agree that it is there,” Fu said.

the fascia of the biceps femoris covers the lateral collateral ligament
Denoted in this anatomic dissection is the lateral side of the left knee. Carefully removing the posterior fibers of the ITB, the casulo-osseous layer of the ITB becomes evident. Also identified in about 30% of such dissections is capsular thickening. As shown, the fascia of the biceps femoris covers the lateral collateral ligament (LCL) while it merges with the capsulo-osseous layer distally.

He said the Kaplan fibers, capsule-osseous layer and the strong superficial IT band form the anterolateral knee complex which form a protective wall around the knee. When the complex is intact, the rest of the knee structures are adequately supported. Procedures, such as extra-articular tenodeses, that reinforce that complex may help to support a well-executed ACL reconstruction, yet they may potentially over-constrain the knee, according to Fu, who is chairman of the Department of Orthopedic Surgery at University of Pittsburgh Medical Center, in Pittsburgh, USA, and an Orthopaedics Today Europe Editorial Board member.

Understands both sides

Andy Williams, MB BS, FRCS, FRCS(Orth), FFSEM(UK), of London, has been on both sides of the debate at different times during his career.

“The so-called ALL probably does exist,” Williams told Orthopaedics Today Europe.

Fresh-frozen cadaveric dissections he and his colleagues did and work they had published in early 2014, right around the same time Claes and colleagues were doing their work on the subject, led Williams to similar conclusions, that a distinct ligament exists.

Williams and colleagues also concluded not all ACL reconstructed knees do well, and they therefore considered it might also be worthwhile to add to that procedure via concurrent surgery done on the outside of the knee. But, according to Williams, authors of early publications may have rushed their work a bit and, in doing so, made some errors in describing the ALL.

Based on results of some of Williams’ more recent studies and tests, he said, “We have found the most important structure is the IT band, specifically its deep capsule-osseous layer, which is attached to the femur by so-called Kaplan fibers. Christoph Kittl, MD,won the Albert Trillat Young Investigator’s Award at the International Society for Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine Biennial Congress in 2015 for this work, which was done in collaboration with Williams and colleagues.

Segond fracture rationale

Amidst claims the Segond fracture is related to the ALL, and may in fact help prove the existence of the ALL, Williams said, “I do not know what causes the Segond [fracture] until it is proven to me. Initially, I wanted to call it the ALL, but, as time has gone by, I have learned that maybe we do not know enough. On the ultrasound, you see something, but do you know it is the ALL?”

Understanding the anterolateral knee structures is far more complex than making a claim the ALL exists because of what occurs during a Segond fracture, according to Williams.

Andy Williams, MB BS, FRCS, FRCS(Orth), FFSEM(UK)
Andy Williams

“It is not as simple as that,” he said.

Methodical, validated research

Williams said some of his early enthusiasm in favor of the ALL was tempered by Andrew A. Amis, DSc(Eng), FIMechE, professor of orthopaedic biomechanics at Imperial College of London, when Williams’ initial work done with Alexander L. Dodds, BSc (Hons), MB BCh, MSc, FRCS (Tr and Orth), started to show the existence of the ALL and the potential need for it to be treated in ACL-injured knees in conjunction with an intra-articular procedure.


“Prof. Amis put the brakes on my excitement to a degree and he is right. If we jump to an operation and get rushed, we miss an opportunity to work it out, paper by paper and step by step. My experience has also been validation of scientific method with my colleagues,” he said.

Williams, who treats many high-level soccer players from around the world, told Orthopaedics Today Europe, the emphasis now should be on what has happened to these patients’ knees in the intervening years. Furthermore, caution is still in order, he said, because lateral extra-articular procedures may be overly promoted by industry and that can influence the direction and extent of the research done in this area.

Long-term findings

Ferretti reported this year at the American Academy of Orthopaedic Surgeons Annual Meeting on clinical and radiological long-term follow-up treating the middle-third of the anterolateral capsule, a term pioneering knee surgeon Jack Hughston, MD, used to describe the anterolateral complex. The study was also published in Arthroscopy.

In chronic cases when the injured capsule could not be visualized arthroscopically, he and colleagues performed non-anatomic reconstruction of the injured ligaments with facia lata. They found better knee stability and few radiological signs of degenerative OA with combined intra-articular and extra-articular reconstructions.

Ferretti said his latest study in Arthroscopy, in which he and colleagues present four classifications for acute anterolateral complex injuries in conjunction with ACL tears, represents his most significant publication in this area to date.

“Besides the high incidence of macroscopic injuries identified at surgery (about 90% of cases), the most important finding was the effect of the direct repair on stability of the knee with disappearance or marked reduction of the pivot shift phenomenon in all cases,” he told Orthopaedics Today Europe.

How to treat ALL

Although the existence of the ALL is controversial, some surgeons are treating this ligament with a variety of techniques, depending on the case.

One of them is Camilo P. Helito, MD, from Brazil, who has no doubt the ALL exists. Among about 100 cadaveric dissections he and colleagues completed, they identified the ALL in nearly every case and Helito has seen the ALL when doing Segond fracture repairs, where there is a ligamentous structure that inserts on the fracture fragment.

He noted the ALL is not present in every person, which he said corresponds to other research showing about 96% of subjects have a structure on the anterolateral portion of the knee that matches the description of the ALL.

Camilo P. Helito, MD
Camilo P. Helito

Biomechanical studies showed the ALL has a synergistic role with the ACL, according to Helito.

“There are a few studies that could not find a major role for this structure, but I believe it is a restrictor for anterolateral tibial rotation,” he told Orthopaedics Today Europe.

Gracilis graft used

In the last few years, Helito has performed ALL reconstructions in some patients with acute or chronic ACL tears, such as high-demand athletes, those who participate in pivoting sports, where he does a combined ACL and ALL reconstruction. The ACL reconstruction is performed arthroscopically, but he uses a minimally invasive approach with small incisions and the remaining portion of a gracilis graft from the ACL surgery fixed with interference screws to reconstruct the ALL.

The patients, who follow the same rehabilitation protocol as if they had only undergone ACL reconstruction, are doing well at about 2-years follow-up, according to Helito. He is now investigating a possible association between lateral meniscus injuries and ALL injuries due to the ALL’s firm attachment to the lateral meniscus, as well as the types of ALL tears that occur in conjunction with chronic or acute ACL tears.

Evaluations done by Williams’ group showed operations or reconstructions done to treat the ALL do not perform well. In fact, Williams said it is not only illogical to place an ALL graft in the location recommended by one company, in particular, that promotes ALL surgery, but it is not likely to work.

“If it does work, it will over-constrain the joint and cause trouble. We found a tenodesis did better,” Williams said.


Future directions

In general, Williams urged orthopaedic surgeons to focus more on the soft tissue envelope with their treatments rather than an isolated ligament. They should also avoid capsular constraint or overtightening should they decide to perform IT band tenodesis or another type of ALL reconstruction, such as one with a stiff graft, to avoid a situation where a patient’s knee develops OA, he said.

As for future work in this area, Fu supports good quality scientific research that is reproducible to independently validate the studies by Claes and others into the ALL. This should be done before proceeding with any clinical trials to prevent any potential harm to patients.

Ferretti would like to see more accurate studies done of the anterolateral complex to help better describe it. He said his own upcoming investigations will involve MRI and ultrasound studies.

“This is one of the future tracks in this field in order to preoperatively detect who requires an additional procedure and additional repair. The amount of the PS test is the best [way] to explore the lateral compartment,” Ferretti said.

“I think the next step for this anterolateral instability subject will be the clinical studies about the ALL reconstruction,” Helito said. – by Susan M. Rapp

Disclosures: Claes and Ferretti report they are paid consultants to Arthrex. Williams reports he is a shareholder in and founder of Fortius Clinic. Fu and Helito report no relevant financial disclosures.