title: Anatomy and Histology of the Knee Anterolateral Ligament.
abstract: BACKGROUND
  Reconstruction of the anterior cruciate ligament (ACL) is one of the most common procedures in orthopaedic surgery. However, even with advances in surgical techniques and implants, some patients still have residual anterolateral rotatory laxity after reconstruction. A thorough study of the anatomy of the anterolateral region of the knee is needed.
  
  
  OBJECTIVE
  To study the anterolateral region and determine the measurements and points of attachments of the anterolateral ligament (ALL).
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Dissections of the anterolateral structures of the knee were performed in 20 human cadavers. After isolating the ALL, its length, thickness, width, and points of attachments were determined. The femoral attachment of the ALL was based on the anterior-posterior and proximal-distal distances from the attachment of the lateral collateral ligament (LCL). The tibial attachment point was based on the distance from the Gerdy tubercle to the fibular head and the distance from the lateral tibial plateau. The ligaments from the first 10 dissections were sent for histological analysis.
  
  
  RESULTS
  The ALL was found in all 20 knees. The femoral attachment of the ALL at the lateral epicondyle averaged 3.5 mm distal and 2.2 mm anterior to the attachment of the LCL. Two distal attachments were observed: one inserts into the lateral meniscus, the other between the Gerdy tubercle and the fibular head, approximately 4.4 mm distal to the tibial articular cartilage. The mean measurements for the ligament were 37.3 mm (length), 7.4 mm (width), and 2.7 mm (thickness). The histological analysis of the ligaments revealed dense connective tissue.
  
  
  CONCLUSIONS
  The ALL is consistently present in the anterolateral region of the knee. Its attachment to the femur is anterior and distal to the attachment of the LCL. Moving distally, it bifurcates at close to half of its length. The ALL features 2 distal attachments, one at the lateral meniscus and the other between the Gerdy tubercle and the fibular head.
  
  
  CONCLUSIONS
  The ALL may be important in maintaining normal rotatory limits of knee motion; ALL rupture could be responsible for rotatory laxity after isolated intra-articular reconstruction of the ACL.
authors.affiliation: Investigation performed at the Department of Orthopedics and Traumatology, Faculty of Medicine, University of São Paulo, São Paulo, Brazil ; Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Camilo Partezani
authors.initials: CP
authors.lastname: Helito
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Marco Kawamura
authors.initials: MK
authors.lastname: Demange
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Marcelo Batista
authors.initials: MB
authors.lastname: Bonadio
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Luis Eduardo Passarelli
authors.initials: LE
authors.lastname: Tírico
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Riccardo Gomes
authors.initials: RG
authors.lastname: Gobbi
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: José Ricardo
authors.initials: JR
authors.lastname: Pécora
authors.affiliation: Department of Orthopaedics and Traumatology, Institute of Orthopedics and Traumatology-Hospital and Clinics, Faculty of Medicine, University of São Paulo (IOT-HCFMUSP), São Paulo, Brazil.
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
keywords: ACL; anatomy; anterolateral ligament; rotatory instability