Systematic Review

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The Structure and Function of the AnterolateralLigament of the Knee: A Systematic Review

Leon Van der Watt, M.D., Moin Khan, M.D., M.Sc., Benjamin B. Rothrauff, M.Res.,Olufemi R. Ayeni, M.D., M.Sc., F.R.C.S.C., Volker Musahl, M.D.,

Alan Getgood, M.D., F.R.C.S.C., and Devin Peterson, M.D., F.R.C.S.C

Purpose: The purpose of this systematic review was to evaluate the anatomic structure and function of the anterolateralligament (ALL) of the knee. Methods: The Medline, Embase, and Cochrane databases were screened for all studiesrelated to the ALL of the knee. Two reviewers independently reviewed all eligible articles and the references of thesearticles. Inclusion and exclusion criteria were applied to all searched studies. Quality assessment was completed for theincluded studies. Results: Nineteen studieswere identified for final analysis. Pooled analysis identified theALL in 430 of 449knees (96%) examined. The ligament was found to originate from the region of the lateral femoral epicondyle and insert onthe proximal tibia midway between the Gerdy tubercle and the fibular head. The ALL was found to be 34.1 to 41.5 mm inlength, 5.1 to 8.3 mm in width above the lateral meniscus, and 8.9 to 11.2 mm in width below the lateral meniscus. By use ofmagnetic resonance imaging, the ALLwas identified in 93%of knees examined (clinical, 64 of 70; cadaveric, 16 of 16). In onecase study the ligament was clearly visualized by ultrasound examination. Histologic analysis across 3 studies showed char-acteristics consistent with ligamentous tissue. Though not shown in biomechanical studies, it is hypothesized that the ALLprovides anterolateral stability to the knee, preventing anterolateral subluxation of the proximal tibia on the femur. One studyidentified a network of peripheral nerves, suggesting a proprioceptive function of the ALL. Conclusions: This systematicreview shows the ALL to be a distinct structure with a consistent origin and insertion sites. The ALL is an extra-articularstructure with a clear course from the lateral femoral epicondyle region, running anteroinferiorly, to the proximal tibia at asite midway between the Gerdy tubercle and the head of the fibula. The function of this ligament is theorized to provideanterolateral knee stability. Level of Evidence: Level IV, systematic review of cadaveric and imaging studies.

he “recently” described structure known as the

Tanterolateral ligament (ALL) was in fact describedin the literature more than 130 years ago in a study byDr. Paul Segond. In 1879 he described “a pearly,

Division of Orthopaedic Surgery, Department of Surgery,niversity (L.V.d.W., M.K., O.R.A., D.P.), Hamilton; Fowlerrt Medicine Clinic, Department of Orthopaedic Surgery, Western.G.), London, Ontario, Canada; and Department of Orthopaediciversity of Pittsburgh (B.B.R., V.M.), Pittsburgh, Pennsylvania,

rs report the following potential conflict of interest or source of.A. receives support from Canadian Institute for Health ResearchNephew. V.M. receives support from ISAKOS/OREF. A.G. re-

rt from Arthrex, SBM Medical, MTF, ISAKOS/OREF, Smith &d ConMed Linvatec.ugust 28, 2014; accepted December 4, 2014.orrespondence to Olufemi R. Ayeni, M.D., M.Sc., F.R.C.S.C.,rthopaedic Surgery, Department of Surgery, McMaster Universitytre, 1200 Main St West, 4E17, Hamilton Ontario, Canada L8N: femiayeni@gmail.comy the Arthroscopy Association of North America/14737/$36.00oi.org/10.1016/j.arthro.2014.12.015

Arthroscopy: The Journal of Arthroscopic and Related S

resistant, fibrous band” associated with an avulsionfracture at the anterolateral proximal tibia as a result offorced internal rotation of the knee.1 This fracture wastermed the “Segond fracture” and is consideredpathognomonic for its association with anterior cruciateligament (ACL) tears.2,3

Management of knee instability including ACLreconstruction is one of the most common orthopaedicprocedures performed, with over 400,000 ACL re-constructions performed in North America annually.4,5

Recent biomechanical investigations suggest thatreconstruction of the ALL may play an important role inknee stability; thus it is essential for surgeons managingknee instability to understand the structure and func-tion of this ligament.6

Since Segond’s first description of this structure, therehave been numerous studies investigating the extra-articular ligamentous structures in and around theknee. Recently, the term “anterolateral ligament” of theknee has been used to describe this structure in a study byVieira et al.7 Although the ALL has been investigated in anumber of other studies, consensus regarding the exact

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570 L. VAN DER WATT ET AL.

structure and function of this ligament remains unclear.The purpose of this studywas to systematically review theliterature and describe the structure and function of theALL. The hypothesis of this study was that the ALL con-tributes significantly to the stability of the knee and it canbe clearly identified by anatomic dissection.

Methods

Identification of StudiesTwo reviewers (L.V.d.W., M.K.) with methodologic

and content expertise independently and in duplicatesearched the Medline, Embase, and Cochrane databasesfor studies published up to and including August 10,2014. The search strategy combined the followingterms: anterolateral ligament, anterior lateral ligament,Segond fracture, lateral capsular ligament, and iliotibialtract. Medical Subject Headings and Emtree headingsand subheadings were used in various combinations inOvid and supplemented with free text to increasesensitivity. The search strategy was adapted in PubMedto include studies E-published ahead of print. Consul-tation with experts, hand searching of the references ofeligible full-text articles, and use of the “related articles”feature in PubMed were all used to identify additionaleligible studies. The abstracts from the past 3 years of 4orthopaedic organizations’ conferences were alsosearched: Canadian Orthopaedic Association; AmericanAcademy of Orthopaedic Surgeons; International Soci-ety of Arthroscopy, Knee Surgery & Orthopaedic SportsMedicine; and the European Society of Sports Trau-matology, Knee Surgery and Arthroscopy.Disagreement regarding data and study inclusion was

resolved by discussion and consensus with a seniorauthor (O.R.A.). Duplicate articles were excluded. Afull-text review of selected studies was then performed.There were no articles requiring translation.

Assessment of Study EligibilityStudies meeting the following inclusion criterion

were included in this review: studies discussing thestructure and/or function of the ALL. The exclusioncriteria were as follows: (1) commentaries, (2) reviewarticles, and (3) non-human studies. There were norestrictions regarding year of publication, type of study,or language.

Data AbstractionData were collected and recorded by one reviewer

(L.V.d.W.) and verified by a second reviewer (M.K.) ina piloted computer spreadsheet program (MicrosoftExcel 2013; Microsoft, Redmond, WA). The followingdata were abstracted from the included studies: authors,date of publication, type of study, sample size, meanage, name of ligament, purpose of study, incidence ofALL, and structure and function of ALL.

Assessment of Methodologic QualityTo our knowledge, no methodologic assessment tool

is available for the evaluation of cadaveric studies. Ascoring system, composed of evaluative criteria for lig-ament structure and function, was developed to assessthe methodologic quality of the cadaveric studies (n ¼15) using input from orthopaedic surgeons andresearch methodologists. As shown in Appendix 1(available at www.arthroscopyjournal.org), items aredivided into 1 of 6 categories: (1) anatomy by dissec-tion; (2) anatomy by imaging; (3) histology; (4)biochemical composition; (5) function, includingbiomechanical properties and clinical examination; and(6) methodologic quality. Because no individual studyis likely to comprehensively examine parameters fallingunder all 6 categories, categorization of similar itemsallows comparison across studies that focus on one or afew categories.Two reviewers (L.V.d.W., M.K.) independently

assessed the methodologic quality of all includedstudies. Observational studies were evaluated with theMethodological Index for Non-Randomized Studies(MINORS), which was developed and validated by Slimet al.8 The ideal MINORS score is 24 for comparativestudies and 16 for non-comparative studies. We gradedall studies for the level of evidence according to theprinciples of evidence-based medicine.9

Data AnalysisAll data abstracted from eligible studies were orga-

nized into a table (Microsoft Word; Microsoft).Descriptive statistics were calculated to reflect the fre-quency of outcome measures.The k statistic was used to examine interobserver

agreement for study eligibility. On the basis of theguidelines of Cohen, a k of 0 to 0.2 represents slightagreement; 0.21 to 0.40, fair agreement; 0.41 to 0.60,moderate agreement; and 0.61 to 0.80, substantialagreement. A value above 0.80 is considered almostperfect agreement.10

Interobserver agreement for methodologic qualityassessment was calculated using the intraclass correla-tion coefficient (ICC). Both the k and ICC were calcu-lated using SPSS statistical analysis software (SPSS,Chicago, IL).

Results

Study IdentificationOur initial electronic literature search identified 1,028

articles. Title and abstract review excluded 227 dupli-cates and 780 studies not related to the ALL. A full-textreview and hand searching of the reference listsexcluded 6 articles and identified 4 additional articles.Nineteen articles were included for final analysis(Fig 1). The k statistic for overall agreement between

Fig 1. Flowchart of literature search.

ANTEROLATERAL LIGAMENT OF KNEE 571

reviewers for the final eligibility decision was 0.87(95% confidence interval, 0.78 to 0.96), indicatingalmost perfect agreement.

Study CharacteristicsThe studies included in this review were conducted

from 1976 to 2014. Of the studies, 7 were purely labo-ratory investigational cadaveric studies6,11-15 (Table 1),8 were mixed studies (3 cadaveric/clinical16-18 and5 cadaveric/imaging19-23), 3 were imaging studies,24-26

and 1 was a clinical observational study27 (Table 2).The total sample size from all 19 studies was 580 (304cadaveric specimens, 164 patients from clinical studies,and 112 patients from imaging studies). Of the 304cadaveric specimens, 95 were fresh frozen, 72 wereembalmed, 26 were fresh, and 111 were not specified.The age at death of the cadaveric specimens ranged from19 to 93 years, with amean age of 71 years. In the clinicalstudies the age of the patients ranged from14 to 60 years,with a mean age of 29 years.The following terms were used to describe the ALL:

“mid-third lateral capsular” ligament by Hughstonet al.27; “lateral capsular” ligament by Johnson,18

Patella et al.,13 and Dietz et al.25; “anterior slip” ofthe lateral collateral ligament by Fulkerson and Gos-sling12; “capsulo-osseous layer” of the iliotibial tract byTerry et al.14; “anterior oblique band” by Irvine et al.17

and Campos et al.19; and “anterolateral ligament” firstintroduced by Vieira et al.7 in 2007. For simplicity, theterm ALL will be used throughout the remainder ofthis article. Nine studies primarily investigated theALL,6,11,15,16,20,22-24,26 five studies analyzed the lateralstructures of the knee,12,13,18,19,27 three studiesfocused on the Segond fracture,17,21,25 and two studiesinvestigated the iliotibial tract at the level of theknee.7,14

Methodologic Quality of Included StudiesAll items of the methodologic index for cadaveric

studies showed consistent scoring between reviewers,with each category total possessing an ICC of 0.985 orhigher (Appendix 1, available at www.arthroscopyjournal.org). The scoring of methodologicquality for the cadaveric studies is shown in Appendix 2(available at www.arthroscopyjournal.org). Items notevaluated in a particular study are marked “not appli-cable”; unavailable scores were excluded from calcula-tions of the mean score for a particular category.The methodologic index for scoring of observational

studies was consistent, with an ICC of 1.00 for all items(Appendix 3, available at www.arthroscopyjournal.org). The scoring of methodologic quality of theobservational studies is shown in Appendix 4 (availableat www.arthroscopyjournal.org). The 7 observational

Table 1. Study Characteristics for Cadaveric Studies

Study Year Type of StudyNo.

ExaminedALL

IdentifiedMean Age,

yr Name of Ligament Purpose of Study Conclusion Related to ALL

Dodds et al.6 2014 Cadaveric: fresh frozen 40 33 of 40 75 Anterolateral ligament Investigating anterolateralstructures of knee

The ALL may control pivot shift andcontribute to rotatory stability.Associated with Segond fracture

Helito et al.15 2013 Cadaveric 20 20 of 20 62 Anterolateral ligament Describe ALL points ofattachment, measurements,and histologic analysis

The ALL attaches anteriorly and distallyto the LCL. It has 2 distalattachments, one at the lateralmeniscus and another between theGerdy tubercle and the fibular head.

Claes et al.11 2013 Cadaveric: embalmed 41 40 of 41 79 Anterolateral ligament Presence and characteristics ofALL

The ALL may control pivot shift and isa distinct ligamentous structure withconsistent origin and insertion sites.Associated with Segond fracture

Vieira et al.7 2007 Cadaveric: fresh 10 Not stated 33-66 Anterolateral ligament Structure of ITT at knee level, aswell as relation to otherstructures

The ALL is a well-defined functionaland anatomic structure.

Patella et al.13 2002 Cadaveric 50 50 of 50 Not stated Lateral capsular ligament Method for lateral plasty tocorrect anterolateral rotatoryinstability

Lateral capsular ligament is a definiteanatomic structure and controls thelateral rotatory stability of the knee.

Terry et al.14 1986 Cadaveric: 17 freshfrozen and 2embalmed

19 19 of 19 19-72 Capsulo-osseous layer of ITT Anatomy of ITT and iliopatellarband

The capsulo-osseous layer of the ITTfunctions as an ALL of the knee. Itprevents anterolateral subluxation ofthe proximal tibia, thus restrainingthe pivot shift.

Fulkerson andGossling12

1980 Cadaveric 24 Not stated Not stated Anterior slip of LCL Analysis of lateral retinacularstructures of knee

This ligament has a distinct origin andinsertion sites.

ALL, anterolateral ligament; ITT, iliotibial tract; LCL, lateral collateral ligament.

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Table 2. Study Characteristics for Mixed Cadaveric, Clinical, and Imaging Studies

Study Year Type of StudyNo.

ExaminedALL

IdentifiedMeanAge, yr Name of Ligament Purpose of Study Conclusion Related to ALL

Claes et al.21 2014 Cadaveric: embalmed 29 29 of 29 81 Anterolateral ligament Relation of Segond fracturewith ALL

The ALL inserts in the proximaltibia from which the Segondfracture avulses. The Segondfracture is a bony avulsion ofthe ALL.

MRI: clinical 19 19 of 19 35Helito et al.23 2014 Cadaveric 10 10 of 10 63 Anterolateral ligament Establish radiographic

landmarks for origin andinsertion of ALL

The ALL was identified in all thespecimens and radiographiclandmarks were established asshown in Table 3.

Radiographs: cadavericRezansoff et al.22 2014 Cadaveric: fresh frozen 13 13 of 13 71 Anterolateral ligament Determine radiographic

landmarks for origin andinsertion of ALL to aid intunnel placement duringALL reconstruction

The radiographic landmarks forthe ALL were described andmay be used for anatomictunnel placement during ALLreconstruction.

Radiographs: cadavericCaterine et al.20 2014 Cadaveric: fresh frozen 19 19 of 19 70 Anterolateral ligament Anterolateral structures of

kneeThe ALL is a distinct ligamentous

structure in the anterolateralaspect of the knee that mayhave a proprioceptive andbiomechanical role incontrolling rotational stability.

MRI: cadaveric 10 10 of 10Vincent et al.16 2012 Cadaveric: fresh 10 10 of 10 85 Anterolateral ligament Incidence, anatomy, and

histology of ALLThe ALL is consistently present

and is a distinct fibrousstructure with a definite originand insertion sites.

Clinical: observational 30 30 of 30Campos et al.19 2001 Cadaveric: fresh frozen 6 6 of 6 74 Anterior oblique band Stabilizing structures on

lateral aspect of kneeand to investigate theSegond fracture

The fibers of the anterior obliqueband contribute to thepathogenesis of the Segondfracture and therefore have astabilizing effect on the knee.

MRI: clinical 17 7 of 12 32MRI: cadaveric 6 6 of 6

Irvine et al.17 1987 Cadaveric 7 7 of 7 35 Anterior oblique band Incidence of Segondfracture and anatomicstructure attached atarea of avulsion

The Segond fracture may occur byavulsion of the anterior obliqueband.

Clinical: observational 8 Not stated

(continued)

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Table 2. Continued

Study Year Type of StudyNo.

ExaminedALL

IdentifiedMeanAge, yr Name of Ligament Purpose of Study Conclusion Related to ALL

Johnson18 1979 Cadaveric: fresh 6 6 of 6 Not stated Lateral capsularligament

Lateral capsular ligamentcomplex: anatomic andsurgical

Lateral capsular ligament injurycontributes to the pivot-shiftsign. Repair of this ligament canimprove anterolateral stabilityof the knee.

Clinical: observational 7 7 of 7Clinical: surgery 30 30 of 30

Hughston et al.27 1976 Clinical 89 Not stated Not stated Mid-third lateralcapsular ligament

Clinical and operativefindings in patients withlateral compartmentinjuries

Anterolateral rotatory instability isprimarily the result of a mid-third lateral capsular ligamenttear and can be accentuated byan associated ACL tear.

Helito et al.26 2014 Imaging: MRI 39 38 of 39 Not stated Anterolateral ligament Efficacy of routine 1.5-TMRI in identifying ALLand describing its pathand relations to lateralknee structures

The ALL can be visualized onroutine 1.5-T MRI scans, withsome part of the ligament seenin 97.4% of scans.

Cianca et al.24 2014 Imaging: US 1 1 of 1 52 Anterolateral ligament US of anterolateralligament of knee

ALL is a distinct structure, clearlyvisible on US examination.

Dietz et al.25 1986 Imaging: radiographs 20 20 of 20 21 Lateral capsularligament

Radiographic appearanceof Segond fracture

The Segond fracture is caused byavulsion of the lateral capsularligament and is differentiatedfrom avulsion fractures of theGerdy tubercle or the fibularhead and from compressionfractures of the lateral tibialplateau.

ACL, anterior cruciate ligament; ALL, anterolateral ligament; MRI, magnetic resonance imaging; US, ultrasound.

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Fig 2. Anterolateral view of a right knee. With the iliotibialtract reflected, the anterolateral ligament (ALL) fibers areclearly visualized to be a distinct ligamentous structure. (FH,fibular head; GT, Gerdy tubercle; LCL, lateral collateral liga-ment; LFE, lateral femoral epicondyle.)

ANTEROLATERAL LIGAMENT OF KNEE 575

studies were all non-comparative studies and werescored out of a total of 16, with mean scores rangingfrom 3 to 10.

Presence of ALLThe presence or absence of the ALL was reported in 16

of the included studies6,11,13-26 (Figs 2-5). In these studiesthe ALL was identified in 430 of 449 knees (96%).The ALL was found to be a distinct ligamentous

structure in 18 of 19 studies. In all of the cadaveric

studies, the structure of the ALL was directly observed;it was identified using ultrasound by Cianca et al.24 andclinically during operative dissection by Hughstonet al.27

Dietz et al.25 in 1986 confirmed the appearance of theSegond fracture and attributed it to an avulsion of theALL. This theory was supported by Irvine et al.17 in1987 in their study investigating 7 cadaveric knees and8 clinical examinations of patients. Campos et al.19 in2001 concluded that the Segond fracture was caused byavulsion of the ALL in a study specifically investigatingthe pathogenesis of the Segond fracture in 7 cadavericknees and magnetic resonance images of 17 patients.Cadaveric studies by Claes et al.11 and Dodds et al.6

investigating the ALL also linked the ALL to theSegond fracture. Claes et al.21 again supported thistheory in a study investigating the relation of theSegond fracture to the ALL.

Structure of ALL

Origin. The origin of the ALL was described in16 included studies (Table 3). Seven studies describedthe origin to be from the lateral femoralepicondyle.11,12,16,18,19,21,27 In the remaining 9studies, slight variation was present regarding theexact site of origin; however, all descriptionsindicated that the ALL bordered the lateral femoralepicondyle.6,7,13-15,20,22,23,26

Anatomic Course. The course of the ALL was describedin 13 studies, describing a passage from the region ofthe lateral femoral epicondyle anteroinferiorly towardthe proximal tibia, obliquely across the knee

Fig 3. Coronal magnetic resonanceimages of a right knee demonstratingthe anatomic location of the lateralcollateral ligament (LCL) on the leftand the anterolateral ligament (ALL)on the right, located more anteriorly tothe LCL.

Fig 4. Coronal magnetic resonance image and frontal view of a dissected left knee demonstrating the Segond fracture. (A)Typical Segond fracture as observed on a frontal magnetic resonance imaging sequence of a left knee. (B) Frontal view ofanterolateral ligament (ALL) in a dissected left knee. The parallel between the location of the Segond fracture bed and the tibialALL insertion can be easily appreciated. The tan arrows depict the ALL on both the magnetic resonance image and cadavericdissection. (ACL, anterior cruciate ligament; LFC, lateral femoral condyle; LM, lateral meniscus.) Reprinted with permission.21

576 L. VAN DER WATT ET AL.

joint.6,7,11-16,19-21,24,26 Dodds et al.6 described the ALLas an extracapsular ligamentous structure superficialto the lateral collateral ligament and the jointcapsule, with branching attachments to the lateralmeniscus. Claes et al.,11 Caterine et al.,20 and Helitoet al.15 confirmed that this ligament had attachmentsto the lateral meniscus.

Insertion. The insertion site of the ALL was consistentlydescribed in 16 studies as the anterolateral proximaltibia, at a point midway between the Gerdy tubercleand the fibular head.6,7,11-17,20-26 In the 3 remaining

studies the descriptions of the insertion site werevague, with Campos et al.19 describing it as the lateralmid portion of the tibia; Johnson,18 the proximaltibia; and Hughston et al.,27 the tibial joint margin.

Ultrasound Appearance. Cianca et al.24 examined thelateral knee of a 52-year-old man with ultrasoundand identified the ALL, best visualized with the kneeat 90� of flexion and internal tibial rotation. Theligament was seen to pass over the lateral meniscusand traveled parallel to the iliotibial tract. The

Fig 5. Three-dimensional recon-structed computed tomography (CT)image and lateral view of a dissectedleft knee showing the association ofthe Segond fracture and the antero-lateral ligament (ALL). (A) Three-dimensional reconstructed CT imageof a Segond fracture in a left knee. (B)Lateral view of ALL in a dissected leftknee. The parallel between the loca-tion of the Segond fracture bed andthe tibial ALL insertion can be easilyappreciated (arrows). *Intercondylareminence fracture. (FH, fibular head;LCL, lateral collateral ligament; LFE,lateral femoral epicondyle.) Reprintedwith permission.21

Table 3. Structure of Anterolateral Ligament

Study Origin Course Insertion Characteristics

Claes et al.21 Lateral femoral epicondyle Depth of lateral tibial synovial recessmeasured 6.5 � 1.5 mm

Anterolateral proximal tibiaGerdy tubercle to ALL: 22 mmFibular head to ALL: 21.3 mm

Gerdy tubercle to Segond fracture:22.4 mm

Insertion width: 11.3 mmHelito et al.23 1.9 � 1.4 mm anterior and 4.1 �

1.1 mm distal to LCLLateral radiograph: 47% fromanterior condyle and 3.7 mminferior to Blumensaat line

AP radiograph: 15.8 mm fromposterior bicondylar line

Not stated 4.4 � 0.8 mm distal to anterolateralproximal tibia, at a point 42% ofthe way from the fibular head tothe Gerdy tubercle

Lateral radiograph: 53% fromanterior tibial plateau

AP radiograph: 7.0 mm from tibialjoint line

Not stated

Helito et al.26 Lateral femoral condyle, immediatelyanterior to LCL

Anteroinferior, superficial to poplitealtendon

Bifurcation 3.0 mm proximal tolateral meniscus

7.0 mm distal to lateral tibial plateau Thin linear structure with thicknessbetween 1 and 3 mm

Rezansoff et al.22 Near lateral femoral epicondyle, at apoint on a line drawn from theposterior femoral cortical line andjust inferior to the Blumensaat line

Not stated 24.7 mm from Gerdy tubercle and11.5 mm distal to lateral tibialplateau, at a point between a linealong the posterior tibial cortex anda parallel line from the apex of thetibial spine, intersecting aperpendicular line from the apex ofthe posterior tibial condyles

Not stated

Caterine et al.20 2 variations: (1) proximal andposterior to lateral epicondyle and(2) anterior and distal to lateralepicondyle

Obliquely within capsule to insert ontibia

Deep attachment to lateral meniscus

Midway between head of fibula andGerdy tubercle

Intracapsular ligamentous thickeningof anterolateral capsule

Dodds et al.6 8 mm proximal and 4.3 mm posteriorto lateral femoral epicondyle

Superficial to LCL and capsule withbranching attachments to meniscus

Midway between head of fibula andGerdy tubercle

Extracapsular ligamentous structure

Cianca et al.24 Not stated Over lateral meniscus, travelingobliquely and parallel to ITT

Inferior to proximal lateral edge oftibia, posterior and proximal toGerdy tubercle

Easiest to identify with 90� of flexionand internal rotation of knee,resulting in ligament being taut

Helito et al.15 2.2 � 1.5 mm anterior and 3.5 �2.1 mm distal to LCL

Bifurcation present at 52.5% of itslength (proximal to distal),attaching to lateral meniscus

4.4 � 1.1 mm distal to lateral tibialplateau, at a point 38% of wayfrom fibular head to Gerdy tubercle

Length: 37.3 � 4.0 mmWidth: 7.4 � 1.7 mmThickness: 2.7 � 0.6 mmHistology: dense connective tissuewith arranged fibers and littlecellular material

Claes et al.11 Lateral femoral epicondyle, anteriorto LCL, proximal and posterior toinsertion of popliteus

Oblique anteroinferior to proximaltibia Attachment to meniscus

In middle of a line connecting Gerdytubercle and tip of fibular head

Length: 41.5 mm (flexion), 38.5 mm(extension)

Width: 8.3 mm (origin), 6.7 mm(joint line), 11.2 mm (insertion)

Thickness: 1.3 mm (joint line)

(continued)

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Table 3. Continued

Study Origin Course Insertion Characteristics

Vincent et al.16 Lateral femoral epicondyle Obliquely anteroinferiorly towardlateral meniscus and tibial plateau

Proximal anterolateral tibia, 5 mmfrom articular cartilage, posterior toGerdy tubercle

Collagenous fibers with dense coreand parallel orientationWidth: 8.2 mmThickness: 2 to 3 mmLength: 34.1 mm

Vieira et al.7 Lateral supraepicondylar regionbordering lateral edge of lateralepicondyle

Oblique course toward proximal tibia Laterally to Gerdy tubercle Well-defined ligamentous structure

Patella et al.13 1.5 cm anterior and superior to lateralepicondyle

Oblique anteroinferior course 1.5 cm posteriorly to Gerdy tubercle Ligamentous structure composed of asuperficial and deep bundle

Campos et al.19 Lateral femoral epicondyle Oblique anteroinferior course Lateral midportion of proximal tibia Thick band of tissue between ITT andLCL at level of lateral tibial plateau

Irvine et al.17 Not stated Not stated Midway between Gerdy tubercle andhead of fibula

Ligamentous structure, strongenough to cause avulsion fractureoff proximal tibia

Terry et al.14 Near lateral epicondyle Oblique course toward proximal tibia Just posterior to Gerdy tubercle onlateral tibial tuberosity

Distinct ligamentous structure

Dietz et al.25 Not stated Not stated A point between Gerdy tubercle andfibular head

Can cause avulsion off tibial condyle(optimal radiograph is straight APradiograph)

Fulkerson and Gossling12 Lateral epicondyle, just anterior toorigin of gastrocnemius

Anteroinferior course Proximal tibia immediately anteriorto fibular head

Not stated

Johnson18 Lateral femoral epicondyle Not stated Proximal tibia Strong ligamentous structureHughston et al.27 Lateral femoral epicondyle Not stated Tibial joint margin Technically strong ligament

ALL, anterolateral ligament; AP, anteroposterior; LCL, lateral collateral ligament; ITT, iliotibial tract.

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terminal end point of the ligament was identifiedinferior to the proximal-lateral edge of the tibia,posterior and proximal to the Gerdy tubercle.

Magnetic Resonance Imaging Appearance. Campos et al.19

used 1.5-T magnetic resonance imaging (MRI) toinvestigate the lateral aspect of the knee. Sixcadaveric knees and 17 patients with Segond fractureson radiography were evaluated. The ALL was foundin the cadaveric dissections to have an anterioroblique course, inserting into the lateral aspect of thetibia. In the 17 patients with Segond fractures, theALL was identified in 7 of 12 patients in whomtransverse images were available. The ALL was foundto be attached to the avulsed fragment of the Segondfracture.Caterine et al.20 studied 10 fresh-frozen knees with 3-T

MRI followed by gross anatomic dissection. In all 10specimens the ALL could be identified as a thin, denseblack structure running obliquely from posterior toanterior, proximal to distal, with respect to the fibularcollateral ligament. As in the gross anatomy findings,some variation was found with respect to the proximalorigin, that is, posterior proximal or anterior distal to thelateral collateral ligament origin. In all 10 specimens theMRIfindingswere consistentwith the anatomic findings.Helito et al.26 evaluated the ability of routine 1.5-T

MRI to identify the ALL. A portion of the ligamentwas identified in 38 of 39 scans (97.4%), and the entireligament was visualized in 28 scans (71.8%).Claes et al.21 evaluated the magnetic resonance im-

ages of 19 patients with Segond fractures and comparedthem with 29 cadaveric knees in which the ALL wasdissected. The distance from the Segond fracture to theGerdy tubercle measured 22.4 mm, whereas the dis-tance from the ALL insertion to the Gerdy tuberclemeasured 22.0 mm. The difference of 0.4 mm was notstatistically significant (P ¼ .7).

Dimensions of ALL. Five studies analyzed the di-mensions of the ALL.11,15,16,20,21 Caterine et al.20 foundthat the mean length in extension was 40.3 � 6.2 mm,whereas Claes et al.11 found that the mean length at90� of flexion was 41.5 � 6.7 mm and the meanlength in extension was 38.5 � 6.1 mm. Helito et al.15

measured the mean length as 37.3 � 4.0 mm, andVincent et al.16 measured it at 90� of flexion as 34.1� 3.4 mm. Caterine et al. measured the width to be5.1 � 1.8 mm above the lateral meniscus and 8.9 �2.5 mm below the meniscus. This compared withClaes et al.,11 who measured the width at the originas 8.3 � 2.1 mm; at the lateral joint line, 6.7 � 3.0mm; and at the insertion, 11.2 � 2.5 mm. The secondstudy by Claes et al.21 measured the insertion widthas 11.3 � 2.8 mm. Helito et al. measured a meanwidth of 7.4 � 1.7, whereas Vincent et al. measured a

mean width of 8.2 � 1.5 mm. The thickness of theALL measured by Caterine et al.20 was 1.4 � 0.6 mm,whereas Claes et al.11 measured it to be 1.3 �0.6 mm after resection of the lateral meniscus. Thethicknesses measured by Helito et al. and Vincentet al. differed slightly, with values of 2.7 � 0.6 mmand 2 to 3 mm, respectively.

Histologic Analysis. Vincent et al.16 performed ahistologic analysis on the ALL. Longitudinal sectionsof the ligament showed wavy collagenous fibers witha parallel orientation, suggestive of ligamentous ortendinous tissue.In the study by Helito et al.,15 histologic analysis of

the ALL showed dense connective tissue with arrangedfibers and minimal cellular material. Caterine et al.20

also showed the ALL to consist of ligamentous tissue,on the basis of the morphology of the collagen fibers onH&E staining. A clear transition from ligamentous tis-sue to mineralized fibrocartilage to bone was found,indicating clear bone-to-bone attachments proximallyand distally. Furthermore, immunohistochemicalstaining for neurofilament protein, a marker of nervousinnervation, identified structures with morphologiccharacteristics of mechanoreceptors, adding evidencethat the ALL is a ligamentous structure.

Function of ALLIn 9 studies the hypothesis was that the primary

function of the ALL is to provide anterolateral stabilityto the knee, preventing the proximal-lateral tibia fromsubluxation anteriorly relative to the distal femur(Table 4).6,7,11,13,14,16,18,20,27 In 4 additional studies theauthors commented that the ALL does provide stabilityto the knee but did not comment on the specificsregarding the stabilizing effect.15,17,19,25

The study by Dodds et al.6 described the biome-chanics in more depth. They found the ligament to beisometric from 0� to 60� of flexion, with a meanchange in length of 1.7 mm (P ¼ .980). With 60� to 90�

of flexion, there was 4.1 mm of shortening (P ¼ .011).With the knee in extension, tibial rotations did notcause any change in length (P > .26). Internal tibialrotation increased the mean length from 3.6 mm at 30�

to 9.9 mm at 90� of flexion (P < .001). External tibialrotation reduced the mean length by 5.9 mm at 90� offlexion (P < .001).Claes et al.11 found the ALL stabilizing force most

significant at 30� and 90� of flexion. Hughston et al.27

concluded that the ALL is a major lateral static sup-port for the knee at 30� of flexion. The lateral meniscusis also stabilized by the ALL, as observed by Vincentet al.16 Helito et al.15 suggested that it might play a rolein lateral meniscal tears.Seven studies linked the ALL to the Segond frac-

ture.6,11,17,19-21,25 The ALL was hypothesized to be the

Table 4. Biomechanics of Anterolateral Ligament

Study Biomechanical Evaluation

Claes et al.21 ALL tightened with tibial internal rotation and knee flexed to 60�

Helito et al.23 Not statedHelito et al.26 Not statedRezansoff et al.22 Not statedCaterine et al.20 ALL observed to tighten with internal rotation of tibia on femur, with increased tension across structure after

sectioning of ACLDodds et al.6 Isometric from 0� to 60�; shortening of 4.1 mm at 60� to 90�; internal tibial rotation increased length, and external

rotation reduced length; internal tibial rotation increased mean length by 3.6 mm to 9.9 mm at 90� of flexion;external tibial rotation reduced mean length by 5.9 mm at 90� of flexion

Cianca et al.24 ALL observed to be tight with knee flexion and tibial internal rotationHelito et al.15 May play a role in lateral meniscal tears; injury to ALL may increase anterolateral rotatory laxityClaes et al.11 Maximal tension during combined flexion and internal rotation of tibia; tense with forced internal rotation at 30�

and 90�

Vincent et al.16 May play a role in prevention of anterior tibial translation; contributes to meniscal stabilityVieira et al.7 Restraint preventing anterolateral subluxation of tibiaPatella et al.13 Controls tibial plateau internal rotationCampos et al.19 The ligament was attached to the avulsed bone fragment on the anterolateral aspect of the proximal tibia and

therefore has a stabilizing effect on the knee.Irvine et al.17 Can cause avulsion off the proximal tibia, known as the Segond fractureTerry et al.14 Prevents anterolateral subluxation of proximal tibia, resisting pivot-shift phenomenonDietz et al.25 Responsible for Segond avulsion fracture off proximal tibiaFulkerson and Gossling12 Not statedJohnson18 Release of the ligament causes anterolateral rotary instability.Hughston et al.27 Major lateral static support for knee at 30�; anterolateral rotatory stability

ACL, anterior cruciate ligament; ALL, anterolateral ligament.

580 L. VAN DER WATT ET AL.

cause of this avulsion fracture, suggesting that a stabi-lizing effect on the knee was performed by the ALL.Caterine et al.20 found a network of peripheral nervesand structures identified through immunohistochem-istry, indicating that the ALL may have a proprioceptivefunction in the knee.

DiscussionThis systematic review identified the ALL to be a

distinct ligamentous structure with a well-definedorigin and insertion sites. Pooled analysis of studiesevaluating the presence of the ALL found it in 96% ofknees examined. Our review identified the origin of theALL to be either the lateral femoral epicondyle or inclose proximity, with a mean footprint width of8.3 mm.11 It has an oblique course, running in ananteroinferior direction to the proximal tibia, with athickness of about 2 mm and mean width at the lateraljoint line of 6.7 mm.11 The insertion site is welldescribed to be at the proximal anterolateral tibia, justdistal to the lateral joint margin, at a point midwaybetween the Gerdy tubercle and the head of the fibula,with a mean footprint insertion width of 11.3 mm.11,21

In general, the methodologic quality of cadavericstudies improved over time, as did the quality ofanatomic dissection (Appendix 2, available at www.arthroscopyjournal.org). Conversely, only a fewcadaveric studies (n ¼ 4) have sought to discern theALL using imaging studies.19,20,22,23 Even fewer studies

investigated the histologic (n ¼ 3) or biochemical (n ¼0) properties of the ligament.15,16,20 Despite broadpronouncement of the importance of the ALL in ante-rolateral knee stability, evidence of ALL function is stilllimited by the lack of dedicated studies on the functionof the ALL.The methodologic quality of clinical studies showed

some improvement over time, with the 3 more recentstudies having higher scores than the earlier studies. Byuse of the MINORS scoring index8 (Appendix 4, avail-able at www.arthroscopyjournal.org), the last 3 studieshad a mean score of 7 of 16 whereas the first 3 studieshad a mean score of 4.3 of 16.The ALL is theorized to provide anterolateral stability

to the knee, preventing the proximal-lateral tibia fromsubluxation anteriorly relative to the femur. Thisfunction may play an important role in preventing thepivot-shift phenomenon when one is examining theknee for ligamentous injury.28 The ALL is believed tobe involved in the avulsion fracture of the proximaltibia called the Segond fracture.6,11,19,21 The presenceof a Segond fracture suggests significant anterolateralknee instability, especially considering its associationwith ACL tears.2,3 Finally, Caterine et al.20 showedhistologic confirmation that the ALL was ligamentousin nature.

Future DirectionsThis systematic review on the ALL provides clinicians

with a comprehensive understanding of the structure

ANTEROLATERAL LIGAMENT OF KNEE 581

and function of this recently popularized ligament. Inthe clinical setting, this knowledge can be used to un-derstand the complexity of structural knee injuriesinvolving the ACL. With the increasing number of ACLreconstruction procedures performed worldwide, itfollows that persistent postoperative anterolateralinstability may be the result of unaddressed ALLinsufficiency. Further clinical trials to evaluate recon-struction techniques and related outcomes are essentialto better understand the functions that this ligamenthas in the knee. A multicenter study by Getgood et al.29

(STAbiLiTY [Standard ACL Reconstruction vs ACL þLateral Extra-Articular Tenodesis Study]) comparingACL reconstruction with and without lateral extra-articular tenodesis in individuals who are deemed tobe at high risk of reinjuring their ACL may help toanswer this question.The presence of a Segond fracture, long known to be

associated with ACL tears, is believed to be linked toavulsion of the ALL’s distal attachment and may resultin significant knee instability.6,11,17,19,21,25 Subse-quently, further analysis is needed to determine therole of concurrent ALL surgery with ACL reconstruc-tion. With the limited research specifically dedicated tothe ALL, there is a need for further biomechanical,clinical, and imaging studies to better define the struc-ture and clinical importance of this ligament.

LimitationsThis systematic review revealed 19 studies related to

the ALL. Heterogeneity does exist among the includedstudies related to the assessment method and date ofpublication, terminology, inclusion criteria, and defini-tions of instability, all of which may affect our ability tomake definitive conclusions. Furthermore, the includedstudies ranged over a period of 38 years, and within thisperiod, the name and definition of the ALL varied.In addition, advances in MRI quality present a form of

identification bias when comparing results by Camposet al.19 from 13 years ago (1.5-T MRI) with recent re-sults by Caterine et al.20 (3-T MRI). Correlation of MRIwith gross anatomic dissection suggests that MRI maybe a useful tool in assessing the presence of ALL injuryin the clinical scenario.A further limitation is that most of the studies were

cadaveric studies. Although these studies are oftennecessary when examining anatomic structures, theknee is a dynamic structure and testing this ligament inisolation may provide a limited understanding of thefunction of the ALL.At present, there is no validated index to evaluate the

quality of in vitro studies investigating the structure andfunction of musculoskeletal tissues. The methodologicindex developed in this review is composed of param-eters reported in a broad range of studies exploringligament structure/function. Although the index does

not include all possible items that could be used todescribe the ALL, it is sufficiently thorough and wasdevised with input from experienced clinicians andresearch methodologists. In addition, similar items weregrouped under 1 of 6 categories, allowing the assess-ment of methodologic quality for a study examiningone or a few aspects of ALL structure and function.Furthermore, the scoring of included studies accordingto the developed index yielded consistent results acrossreviewers, as shown by very high ICCs. Nevertheless,the index needs to be further validated before generaladoption can be recommended.Using the MINORS, we evaluated the 7 observational

studies. Even though more recent studies did scorehigher using this index, the mean score of the studieswas fairly low.

ConclusionsThis systematic review shows the ALL to be a distinct

structure with a consistent origin and insertion sites.The ALL is an extra-articular structure with a clearcourse from the lateral femoral epicondyle region,running anteroinferiorly, to the proximal tibia at a sitemidway between the Gerdy tubercle and the head ofthe fibula. The function of this ligament is theorized toprovide anterolateral knee stability.

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épanchements sanguins du genou par entorse. Progres Med1879;7:297-341.

2. Goldman AB, Pavlov H, Rubenstein D. The Segond frac-ture of the proximal tibia: A small avulsion that reflectsmajor ligamentous damage. AJR Am J Roentgenol1988;151:1163-1167.

3. Hess T, Rupp S, Hopf T, Gleitz M, Liebler J. Lateral tibialavulsion fractures and disruptions to the anterior cruciateligament. A clinical study of their incidence and correla-tion. Clin Orthop Relat Res 1994;(303):193-197.

4. Junkin DM Jr. Knee ligament injuries. In: Orthopaedicknowledge update: Sports medicine 4. Rosemont, IL: Amer-ican Academy of Orthopaedic Surgeons, 2009;135-146.

5. Oh YK, Kreinbrink JL, Ashton-Miller JA, Wojtys EM.Effect of ACL transection on internal tibial rotation in anin vitro simulated pivot landing. J Bone Joint Surg Am2011;93:372-380.

6. Dodds AL, Halewood C, Gupte CM, Williams A, Amis AA.The anterolateral ligament: Anatomy, length changes andassociation with the Segond fracture. Bone Joint J 2014;96:325-331.

7. Vieira EL, Vieira EA, da Silva RT, Berlfein PA, Abdalla RJ,Cohen M. An anatomic study of the iliotibial tract.Arthroscopy 2007;23:269-274.

8. Slim K, Nini E, Forestier D, Kwiatkowski F, Panis Y,Chipponi J. Methodological Index for Non-RandomizedStudies (MINORS): Development and validation of anew instrument. ANZ J Surg 2003;73:712-716.

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9. Panesar SS, Philippon MJ, Bhandari M. Principles ofevidence-based medicine. Orthop Clin North Am 2010;41:131-138.

10. McHugh ML. Interrater reliability: The kappa statistic.Biochem Med (Zagreb) 2012;22:276-282.

11. Claes S, Vereecke E, Maes M, Victor J, Verdonk P,Bellemans J. Anatomy of the anterolateral ligament of theknee. J Anat 2013;223:321-328.

12. Fulkerson JP, Gossling HR. Anatomy of the knee jointlateral retinaculum. Clin Orthop Relat Res 1980;153:183-188.

13. Patella V, Bernardi S, Moreti B, Pesce V, Simone C.Anatomic reconstruction of the lateral capsular liga-ment (“one-loop plasty”) for anterolateral rotatoryinstability. A cadaveric study. J Orthop Traumatol2002;3:27-29.

14. Terry GC, Hughston JC, Norwood LA. The anatomy of theiliopatellar band and iliotibial tract. Am J Sports Med1986;14:39-45.

15. Helito CP, Demange MK, Bonadio MB, et al. Anatomyand histology of the knee anterolateral ligament. Orthop JSports Med 2013;1:2325967113513546.

16. Vincent JP, Magnussen RA, Gezmez F, et al. The antero-lateral ligament of the human knee: An anatomic andhistologic study. Knee Surg Sports Traumatol Arthrosc2012;20:147-152.

17. Irvine GB, Dias JJ, Finlay DB. Segond fractures of thelateral tibial condyle: Brief report. J Bone Joint Surg Br1987;69:613-614.

18. Johnson LL. Lateral capsular ligament complex:Anatomical and surgical considerations. Am J Sports Med1979;7:156-160.

19. Campos JC, Chung CB, Lektrakul N, et al. Pathogenesis ofthe Segond fracture: Anatomic and MR imaging evidenceof an iliotibial tract or anterior oblique band avulsion.Radiology 2001;219:381-386.

20. Caterine S, Litchfield R, JohnsonM, Chronik B, Getgood A.A cadaveric study of the anterolateral ligament: Re-introducing the lateral capsular ligament. Knee Surg SportsTraumatol Arthrosc in press, available online 15 June, 2014.doi:10.1007/s00167-014-3117-z.

21. Claes S, Luyckx T, Vereecke E, Bellemans J. The Segondfracture: A bony injury of the anterolateral ligament ofthe knee. Arthroscopy 2014;30:1475-1482.

22. Rezansoff AJ, Caterine S, Spencer L, Tran MN, LitchfieldRB, Getgood AM. Radiographic landmarks for surgicalreconstruction of the anterolateral ligament of the knee.Knee Surg Sports Traumatol Arthrosc in press, available on-line 17 June, 2014. doi:10.1007/s00167-014-3126-y.

23. Helito CP, Demange MK, Bonadio MB, et al. Radiographiclandmarks for locating the femoral origin and tibialinsertion of the knee anterolateral ligament. Am J SportsMed 2014;42:2356-2362.

24. Cianca J, John J, Pandit S, Chiou-Tan FY. Musculoskeletalultrasound imaging of the recently described anterolateralligament of the knee. Am J Phys Med Rehabil 2014;93:186.

25. Dietz GW, Wilcox DM, Montgomery JB. Segond tibialcondyle fracture: Lateral capsular ligament avulsion.Radiology 1986;159:467-469.

26. Helito CP, Helito PV, Costa HP, et al. MRI evaluation ofthe anterolateral ligament of the knee: Assessment inroutine 1.5-T scans. Skeletal Radiol 2014;43:1421-1427.

27. Hughston JC, Andrews JR, Cross MJ, Moschi A. Classifi-cation of knee ligament instabilities. Part II. The lateralcompartment. J Bone Joint Surg Am 1976;58:173-179.

28. Musahl V, Hoshino Y, Ahlden M, et al. The pivot shift: Aglobal user guide. Knee Surg Sports Traumatol Arthrosc2012;20:724-731.

29. Getgood A. Standard ACL reconstruction vs ACL þ lateralextra-articular tenodesis study (STAbiLiTY). Available athttps://clinicaltrials.gov/ct2/show/NCT02018354?term¼stabilityþANDþgetgood&rank¼1. Accessed July 31, 2014.

Appendix 1. Methodologic Index for Cadaveric Studies

Score ICC

1. AnatomyddissectionA. Insertion sitei. Dimensions (height, width)a. Femoral 0.980b. Tibial 0.982ii. Anatomic location (relative to other structures)a. Femoral 0.984b. Tibial 1.000

B. Ligament midsubstancei. Dimensions (height, width, length) 0.950ii. Anatomic location (relative to other structures) 0.736

Anatomyddissection total score (out of 18) 0.9962. Anatomydnoninvasive imaging (e.g., MRI, ultrasound)

A. Insertion sitei. Dimensions (height, width)a. Femoral 1.000b. Tibial 1.000ii. Anatomic location (relative to other structures)a. Femoral 0.985b. Tibial 1.000

B. Ligament midsubstancei. Dimensions (height, width, length) 1.000ii. Anatomic location (relative to other structures) 0.861

Anatomydimaging total score (out of 18) 0.9853. Histology

A. Tissue structure (e.g., H&E, trichrome) 1.000B. Insertion site (e.g., bone-ligament interface with transitional

fibrocartilage)1.000

C. Collagen fibril alignment (e.g., polarized light microscopy, SEM) 1.000D. Collagen fibril diameter (e.g., TEM) 1.000E. Cellularity (e.g., nuclei per high-power field) 1.000F. Vascularity (e.g., immunohistochemistry for CD31, CD34, vWF) 1.000G. Innervation (e.g., immunohistochemistry for NFP) 1.000H. Fibroblast phenotype (e.g., Scleraxis, Tenomodulin) 1.000I. Other extracellular matrix proteins (e.g., Tenascin C, elastin) 1.000

Histology total score (out of 27) 1.0004. Biochemical composition

A. Total collagen (e.g., hydroxyproline assay) 1.000B. Proteoglycan (e.g., dimethylmethylene blue assay) 1.000C. Collagen cross-links (e.g., pyridinoline assay) 1.000D. Type I collagenetype III collagen ratio 1.000

Biochemical composition total score (out of 12) 1.0005. Function

A. Tensile loading (0, not reported; 1, reported)i. Ultimate load 1.000ii. Stiffness 1.000iii. Ultimate stress 1.000iv. Young modulus 1.000v. Viscoelastic properties (e.g., relaxation constants) 1.000

B. Joint kinematicsdin situ ALL length at various joint angles/loadingconditions (0 to 3 points)

1.000

C. Joint kinematicsdin situ ALL forces at various joint angles/loadingconditions (0 to 3 points)

1.000

D. Clinical examination (0, not reported; 1, reported)i. Anterior drawer 1.000ii. Slocum test 1.000iii. Lachman test 1.000iv. Pivot shift 1.000

Function total score (out of 15) 1.0006. Methodologic quality*

A. Clearly stated purpose (i.e., suggested but not explicitly stated, 1 point) 1.000B. Clear description of methods (i.e., so as to be independently replicated) 0.920

(continued)

ANTEROLATERAL LIGAMENT OF KNEE 582.e1

Appendix 1. Continued

Score ICC

C. Appropriate experimental design (e.g., sufficient sample size, controls,statistical analyses)

1.000

D. ALL identified as distinct structure (relative to surrounding structures) 1.000E. Clear description of preservation method (e.g., fresh-frozen, embalmed) 1.000

Methodologic quality total score (out of 10) 0.997

NOTE. Unless otherwise indicated, each item is scored as follows: 0, not reported; 1, qualitative (descriptive, incomplete); 2, qualitative(descriptive, complete) or quantitative (incomplete); or 3, quantitative (complete).ALL, anterolateral ligament; CD, cluster of differentiation; ICC, intraclass correlation coefficient; MRI, magnetic resonance imaging; NFP,

neurofilament protein; SEM, scanning electron microscopy; TEM, transmission electron microscopy; vWF, von Willebrand factor.*Scored as follows: 0, not reported; 1, reported but inadequate; or 2, reported and adequate.

582.e2 L. VAN DER WATT ET AL.

Appendix 2. Mean Scores of Cadaveric Studies Based on Methodologic Index

StudyAnatomydDissection

(out of 18)AnatomydImaging

(out of 18)Histology(out of 27)

BiochemicalComposition(out of 12)

Function(out of 15)

Methodologic Quality(out of 10)

Claes et al.21 8 6 NA NA 1 10Helito et al.23 8.5 8 NA NA NA 8Rezansoff et al.22 8.5 8 NA NA NA 10Caterine et al.20 13.5 3.5 12 NA 1 10Dodds et al.6 14.5 NA NA NA 4 10Helito et al.15 11.5 NA 4 NA NA 7.5Claes et al.11 16 NA NA NA 3 10Vincent et al.16 8.5 NA 5 NA 3 10Vieira et al.7 3 NA NA NA NA 9Patella et al.13 3 NA NA NA 2 4Campos et al.19 3 5 NA NA NA 9Irvine et al.17 2 1 NA NA 2 4Terry et al.14 3 NA NA NA NA 7Fulkerson and

Gossling123 NA NA NA NA 5

Johnson18 4 NA NA NA 5 7Mean score 7.3 5.3 7.0 NA 2.6 8.0

NA, not applicable.

Appendix 3. Methodological Index for Non-Randomized Studies (MINORS)8

Score ICC

Methodologic items for non-randomized studies1. A clearly stated aim: The question addressed should be precise and relevant in light of the available

literature.1.000

2. Inclusion of consecutive patients: All patients potentially fit for inclusion (satisfying the criteria forinclusion) have been included in the study during the study period (details about the reasons forexclusion or no exclusions).

1.000

3. Prospective collection of data: Data were collected according to a protocol established before the beginningof the study.

1.000

4. Endpoints appropriate to the aim of the study: An unambiguous explanation of the criteria used to evaluatethe main outcome is provided, which should be in accordance with the question addressed by the study.In addition, the endpoints should be assessed on an intention-to-treat basis.

1.000

5. Unbiased assessment of the study endpoint: Blind evaluation of objective endpoints and double-blindevaluation of subjective endpoints should be performed. Otherwise, the reasons for not blinding shouldbe stated.

1.000

6. Follow-up period appropriate to the aim of the study: The follow-up should be sufficiently long to allow theassessment of the main endpoint and possible adverse events.

1.000

7. Loss to follow-up <5%: All patients should be included in the follow-up. Otherwise, the proportion lost tofollow-up should not exceed the proportion in whom the major endpoint occurred.

1.000

8. Prospective calculation of the study size: Information should be provided on the size of detectabledifference of interest with a calculation of the 95% confidence interval, according to the expectedincidence of the outcome event, and information should be provided about the level for statisticalsignificance and estimates of power when comparing the outcomes.

1.000

Total score (out of 16) 1.000Additional criteria in the case of a comparative study

9. An adequate control group: Having a gold-standard diagnostic test or therapeutic intervention recognizedas the optimal intervention according to the available published data

NA

10. Contemporary groups: The control and studied groups should be managed during the same period (nohistorical comparison).

NA

11. Baseline equivalence of groups: The groups should be similar regarding the criteria other than the studiedendpoints. Confounding factors that could bias the interpretation of the results should be absent.

NA

12. Adequate statistical analyses: Whether the statistics were in accordance with the type of study withcalculation of confidence intervals or relative risk

NA

Total score (out of 24) NA

NOTE. Data scored as follows: 0, not reported; 1, reported but inadequate; or 2, reported and adequate.ICC, intraclass correlation coefficient; NA, not applicable.

Appendix 4. Mean Scores of Clinical Studies Based on Methodologic Index

StudyClear Aim(out of 2)

ConsecutivePatients (out

of 2)

ProspectiveData (out of

2)

EndpointsAppropriate(out of 2)

UnbiasedEndpoints(out of 2)

Follow-upAppropriate(out of 2)

Loss toFollow-up(out of 2)

ProspectiveStudy Size(out of 2)

Total Score(out of 16)

Helito et al.26 2 1 2 2 0 0 0 0 7Cianca et al.24 2 1 1 2 0 0 0 0 6Vincent et al.16 2 2 2 2 0 0 0 0 8Irvine et al.17 2 2 2 1 0 2 1 0 10Dietz et al.25 1 0 2 1 0 0 0 0 4Johnson18 1 0 1 1 0 0 0 0 3Hughston et al.27 2 2 0 2 0 0 0 0 6

ANTEROLATERAL LIGAMENT OF KNEE 582.e3