INTRODUCTION
Over the past four years there has been a resurgence in interest about a small little lateral ligament of the knee known as the anterolateral ligament (ALL). I’m not even sure I remember learning much about it during school, but with the number of ACL reconstructions associated with chronic rotational instability rising, researchers and surgeons have been diverting focus to understand what impact an ALL-deficient knee has on ACL recovery and regaining rotational stability.
The ligament was first published in 1879, when French Surgeon Paul Segond described the ALL in-relation to an avulsion fracture known as a Segond Fracture (Pomajzl et al., 2015). For a long time there remained a paucity in the literature about the exact anatomy, histology and biomechanical function of the ALL. In 2015, Pomajzl et al conducted a systematic review on all articles prior to 2014 about the ALL. Only 13 papers met the inclusion criteria, but what these articles confirmed, is that there were several studies clearly defining the ALL as a distinct ligament and not a fibrous branch of the LCL or ITB. It was around this time that the ALL made its way back onto the map of the knee. The remainder of this blog is a refresher about the anatomy and biomechanical function of the ALL and what we currently know to be true about it’s role in rotational stability of the knee.
ANATOMY
The anterolateral ligament (ALL) of the knee is a distinct ligament, separate to the lateral collateral ligament, that has fibres which span obliquely over the LCL connecting the lateral femoral condyle to Gerdy’s tubercle on the tibia (Bonanzinga et al., 2017). Vincent et al (2012, p.147) describe the anatomy in greater detail stating that:
- The ALL begins near or on the poplitus tendon insertion on the lateral femoral condyle.
- It inserts into the lateral meniscus and the tibial plateau 5mm distal to the articular surface and posterior to Gerdy’s tubercle.
- The average width is 8.3mm ± 1.5 mm.
- The average length is 34.1 ± 3.4mm.
The ALL is not an anatomical anomaly, which begs the question as to why we seemed to have forgotten about it? Vincent et al (2012) found the ALL present in 100% of the test sample. These authors dissected 30 knees to find the ALL and after understanding its anatomical connections further, proposed that the ALL plays an important role in stability of the lateral meniscus “even in the absence of ACL pathology, including limiting anteroposterior translation during flexion and preventing meniscal extrusion” (Vincent et al, 2012., p.156). These statistics are consistent with other papers published in more recent years (Farhan, et al., 2017).
Image source: (Vincent et al., 2012, p. 149)
Bonanzinga et al (2017a) published two papers after dissecting 10 fresh-frozen knees to establish the role that the anterolateral ligament (ALL) of the knee plays in rotational stability compared to the anterior cruciate ligament (ACL). What these authors found is that the ALL plays a key role in stabilization of tibial internal rotation but less anterior translation at the knee. They used three common clinical tests, the anterior draw, Lachman’s and pivot shift test to detect different degrees of stability in an ACL-impaired versus ACL & ALL - impaired knee. From these test conditions the authors were able to conclude that ‘the ALL plays a significant role in controlling static internal rotation and acceleration during pivot shift test… but, ALL resection does not produce any significant change in terms of anterior displacement’ (Bonanzinga et al., 2017a, p.1055). What this means is that the ALL plays a significant role as a biomechanical restraint to knee internal rotation. Holger Drews et al (2017) further specified that the ALL has the highest impact on rotational stability between 60-120 degrees of knee flexion.
Song et al (2017) looked more closely at the correlation between instability on the pivot shift test and the prevalence of ALL injury on MRI. These authors found that when using the pivot shift test to assess an ACL-deficient knee, there is a strong correlation between more severe gradings on the pivot shift test and the presence of GR II and III injuries of the ALL. Interestingly, they also found that lateral compartment contusion was more commonly found in patients with a concomitant ALL injury.
CLINICAL RELEVANCE
As there has been some confusion about the anatomy and function of the ALL in recent years, many specialists are urging clinicians to consider the role of the ALL in anterolateral rotational stability of the knee, but also cautioning them to consider that many other structures contribute to this stability as well. These structures include the ITB, lateral meniscus, ACL and lateral capsule. It may be more helpful to be assessing these combines structures as an “anterolateral complex” of the knee than individual structures and to remember that ligamentous injury, meniscal lesions and bony morphology can all contribute to instability (Musahl, et al., 2017). Interestingly, while some authors have proposed that the ALL plays an important role to stability of the lateral meniscus (Vincent, et al., 2012), a lateral meniscal injury is associated with delayed ACL surgery rather than increases rotational instability (Hardy, et al., 2017).
The goal of ACL reconstruction surgery is to abolish rotational and anterior translatory instability, detected on tests like the pivot shift and Lachman’s tests. Not all patients are able to abolish this instability following reconstruction, with 25-38% of patients continuing to have rotational instability (Hardy, et al, 2017, p1118).
Theoretically, if the ALL plays an important role in knee stability, then surgical reconstruction of the ALL in combination with an ACLR would be logical in the ACL+ALL deficient knee. This would require changes to the current surgical technique involving a tendon graft from semitendinosis to reconstruct the ALL. Although this additional reconstruction is not standard practice, research is emerging to suggest that both reconstructions result in reduced rotational instability on the pivot shift test when a concomitant ALL injury is present (Bonanzingo et al., 2017b; Hardy et al., 2017). It appears that the patients who benefit most from this procedure sustained their injury under an explosive rotational mechanism, have a Segond fracture (makes sense) and exhibit >10mm of anterior translation during the anterior draw test (Hardy, et al., 2017, p.1118).
Not all articles recommend surgical reconstruction (Stentz-Olesen., et al, 2017) but when reading such papers further it appears that the knees that were investigated were cadavers. Personally, I think it is difficult to know how much research from a non-living knee can be applied to or correlated with clinical instability in a live subject. Just something to keep in mind.
Definitely a shorter blog this week from us, but hopefully an important reminder that coming back to anatomy can help us further understand the finer detail of injury management and improve our changes of successful rehabilitation.
Sian - via Rayner and Smale
Sian Smale is an Australian-trained Musculoskeletal Physiotherapist. Sian completed her Bachelor of Physiotherapy through La Trobe University in 2009 and in 2013 was awarded a Masters in Musculoskeletal Physiotherapy through Melbourne University. Since graduating from her Masters program, Sian has been working in a Private Practice setting and writing a Physiotherapy Blog "Rayner & Smale". Prior to moving to San Francisco, Sian worked at Physical Spinal and Physiotherapy Clinic and has a strong background in manual therapy and management of spinal spine, headaches and sports injuries. Since moving to the Bay area, Sian has become a Physiotherapist for the Olympic Winter Institute of Australia, traveling with their Para Alpine teams. Sian currently works full time at TherapydiaSF as a physical therapist and clinical pilates instructor.
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REFERENCES:
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Bonanzinga, T., Signorelli, C., Grassi, A., Lopomo, N., Jain, M., Mosca, M., ... & Zaffagnini, S. (2017b). Kinematics of ACL and anterolateral ligament. Part II: anterolateral and anterior cruciate ligament reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy, 25(4), 1062-1067.
Cavaignac, E., Wytrykowski, K., Reina, N., Pailhé, R., Murgier, J., Faruch, M., & Chiron, P. (2016). Ultrasonographic identification of the anterolateral ligament of the knee. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 32(1), 120-126.
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Lording, T., Stinton, S. K., Neyret, P., & Branch, T. P. (2017). Diagnostic findings caused by cutting of the iliotibial tract and anterolateral ligament in an ACL intact knee using a standardized and automated clinical knee examination. Knee Surgery, Sports Traumatology, Arthroscopy, 25(4), 1161-1169.
Musahl, V., Getgood, A., Neyret, P., Claes, S., Burnham, J. M., Batailler, C., ... & Karlsson, J. (2017). Contributions of the anterolateral complex and the anterolateral ligament to rotatory knee stability in the setting of ACL Injury: a roundtable discussion. Knee Surgery, Sports Traumatology, Arthroscopy, 25(4), 997-1008.
Neri, T., Palpacuer, F., Testa, R., Bergandi, F., Boyer, B., Farizon, F., & Philippot, R. (2017). The anterolateral ligament: Anatomic implications for its reconstruction. The Knee, 24(5), 1083-1089.
Pomajzl, R., Maerz, T., Shams, C., Guettler, J., & Bicos, J. (2015). A review of the anterolateral ligament of the knee: current knowledge regarding its incidence, anatomy, biomechanics, and surgical dissection. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 31(3), 583-591.
Smeets, K., Slane, J., Scheys, L., Forsyth, R., Claes, S., & Bellemans, J. (2017). The Anterolateral Ligament Has Similar Biomechanical and Histologic Properties to the Inferior Glenohumeral Ligament. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 33(5), 1028-1035.
Smeets, K., Bellemans, J., Scheys, L., Eijnde, B. O., Slane, J., & Claes, S. (2017). Mechanical Analysis of Extra-Articular Knee Ligaments. Part two: Tendon grafts used for knee ligament reconstruction. The Knee.
Song, G. Y., Zhang, H., Wu, G., Zhang, J., Liu, X., Xue, Z., ... & Feng, H. (2017). Patients with high-grade pivot-shift phenomenon are associated with higher prevalence of anterolateral ligament injury after acute anterior cruciate ligament injuries. Knee Surgery, Sports Traumatology, Arthroscopy, 25(4), 1111-1116.
Stentz-Olesen, K., Nielsen, E. T., de Raedt, S., Jørgensen, P. B., Sørensen, O. G., Kaptein, B., ... & Stilling, M. (2017). Reconstructing the anterolateral ligament does not decrease rotational knee laxity in ACL-reconstructed knees. Knee Surgery, Sports Traumatology, Arthroscopy, 25(4), 1125-1131.
Van der Watt, L., Khan, M., Rothrauff, B. B., Ayeni, O. R., Musahl, V., Getgood, A., & Peterson, D. (2015). The structure and function of the anterolateral ligament of the knee: a systematic review. Arthroscopy: The Journal of Arthroscopic & Related Surgery, 31(3), 569-582.
Vincent, J. P., Magnussen, R. A., Gezmez, F., Uguen, A., Jacobi, M., Weppe, F., ... & Neyret, P. (2012). The anterolateral ligament of the human knee: an anatomic and histologic study. Knee Surgery, Sports Traumatology, Arthroscopy, 20(1), 147-152.
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