title: Does limited internal femoral rotation increase peak anterior cruciate ligament strain during a simulated pivot landing?
abstract: BACKGROUND
  Many factors contributing to anterior cruciate ligament (ACL) injury risk have been investigated. Recently, some ACL-injured individuals have presented with a decreased range of hip internal rotation compared with controls. The pathomechanics of why decreased hip range of motion increases risk of ACL injury have not yet been studied.
  
  
  OBJECTIVE
  Peak relative strain of the anteromedial bundle of the ACL (AM-ACL) during a simulated single-leg pivot landing is inversely related to the available range of internal femoral rotation.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A series of pivot landings were simulated in 10 female and 10 male human knee specimens with a testing apparatus that applied a 2-bodyweight impulsive load, inducing knee compression, flexion moment, and internal tibial torque. The range of internal femoral rotation was (1) locked at ~0°, (2) limited with a hard stop to ~7°, (3) limited with a hard stop to ~11°, or (4) free, with rotation resisted by 2 springs to simulate the resistance of the active hip rotator muscles to stretch. The AM-ACL strain was quantified with a differential variable reluctance transducer. A linear mixed model was used to determine whether a significant linear relation existed between peak AM-ACL relative strain and range of internal femoral rotation.
  
  
  RESULTS
  Peak AM-ACL relative strain was inversely related to the available range of internal femoral rotation (R (2) = 0.91; P < .001), with strain increasing 1.3% for every 10° decrease in rotation; this represented a 20% increase in peak relative strain, given an average range of femoral rotation of 15° upon landing in healthy athletes.
  
  
  CONCLUSIONS
  Peak AM-ACL relative strain was inversely proportional to the available range of internal femoral rotation during simulated single-leg pivot landings.
  
  
  CONCLUSIONS
  Decreased range of internal femoral rotation results in greater ACL strain and may therefore increase the susceptibility to ACL rupture with athletic cutting and pivoting activities. Screening for a limited range of hip internal rotation should therefore become a component of not only ACL injury prevention programs but also evaluation protocols for those with ACL injuries and/or reconstructions.
authors.affiliation: School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA mbeaulie@umich.edu.
authors.forename: Mélanie L
authors.initials: ML
authors.lastname: Beaulieu
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Youkeun K
authors.initials: YK
authors.lastname: Oh
authors.affiliation: Department of Orthopaedic Surgery and MedSport, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Asheesh
authors.initials: A
authors.lastname: Bedi
authors.affiliation: School of Kinesiology, University of Michigan, Ann Arbor, Michigan, USA Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, USA Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: James A
authors.initials: JA
authors.lastname: Ashton-Miller
authors.affiliation: Department of Orthopaedic Surgery and MedSport, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Wojtys
mesh_terms: D016118:Anterior Cruciate Ligament / Q000502:physiology*; D005260:Female; D005269:Femur / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D012399:Rotation; D012737:Sex Factors; D013314:Stress, Mechanical
keywords: anterior cruciate ligament; femoroacetabular impingement; hip; knee; strain