title: Structural Properties of the Anterolateral Capsule and Iliotibial Band of the Knee.
abstract: BACKGROUND
  The role of the anterolateral capsule in knee stability has recently been advocated by studies reporting that a distinct ligament exists in this area. Defining the structural properties of the anterolateral capsule can provide insight into its contribution to joint stability. The structural properties of the iliotibial band also need to be determined, as it is a common graft used for extra-articular tenodesis.
  
  
  OBJECTIVE
  The purpose of this study was to determine the structural properties of the anterolateral capsule and iliotibial band. The hypothesis was that the iliotibial band will have comparable structural properties to the anterolateral capsule because it is generally an accepted graft for extra-articular reconstruction surgeries.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Nine human cadaveric knees (average age, 57 ± 10 years) were dissected to assess the presence of a discrete capsular thickness originating from the lateral femoral epicondyle to the lateral tibial plateau between the Gerdy tubercle and the fibular head. For each knee, 2 constructs were prepared: (1) a bone-anterolateral capsule-bone specimen and (2) a strip of iliotibial band attached to the Gerdy tubercle. Structural properties, including ultimate load, ultimate elongation, and stiffness, were determined for the anterolateral capsule and the iliotibial band. After tensile testing, plain radiographs were obtained for evaluation of the Segond fracture. A paired t test was used to compare the structural properties of the anterolateral capsule with the iliotibial band. Significance was set at P < .05.
  
  
  RESULTS
  Two of the 9 specimens were found to have a discrete thickening of the anterolateral capsule. The iliotibial band had almost 50% higher ultimate load and nearly 3 times higher stiffness (487.9 ± 156.9 N and 73.2 ± 24.1 N/mm, respectively) compared with the anterolateral capsule (319.7 ± 212.6 N and 26.0 ± 11.5 N/mm, respectively) (P < .05 for both). The anterolateral capsule had about double the ultimate elongation compared with the iliotibial band (15.5 ± 7.3 and 8.6 ± 1.4 mm, respectively; P < .05).
  
  
  CONCLUSIONS
  The anterolateral capsule demonstrated significantly reduced structural properties compared with the iliotibial band. The anterolateral capsule did not have a higher ultimate load compared with the posteromedial capsule as reported in the literature.
  
  
  CONCLUSIONS
  The decision to perform an extra-articular reconstruction using an iliotibial band graft should be considered carefully. Unnecessary reconstructions using soft tissue grafts with structural properties that far exceed that of the anterolateral capsule may result in overconstraint of the ACL-reconstructed knee.
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Ata A
authors.initials: AA
authors.lastname: Rahnemai-Azar
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: R Matthew
authors.initials: RM
authors.lastname: Miller
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Guenther
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Freddie H
authors.initials: FH
authors.lastname: Fu
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Bryson P
authors.initials: BP
authors.lastname: Lesniak
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Volker
authors.initials: V
authors.lastname: Musahl
authors.affiliation: Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA genesis1@pitt.edu.
authors.forename: Richard E
authors.initials: RE
authors.lastname: Debski
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D003238:Connective Tissue / Q000033:anatomy & histology*; D005206:Fascia Lata / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000033:anatomy & histology*; D007719:Knee Joint / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged
keywords: anterior cruciate ligament; anterolateral capsule; anterolateral ligament; biomechanical properties; iliotibial band