title: Altered tibiofemoral kinematics in the affected knee and compensatory changes in the contralateral knee after anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Previous studies of knee kinematics after anterior cruciate ligament (ACL) reconstruction have generally employed low-effort tasks and typically not assessed changes in kinematics over time.
  
  
  OBJECTIVE
  (1) During single-legged hop landing, ACL-reconstructed limbs will have altered kinematics compared with contralateral (ACL-intact) limbs 5 months after surgery. (2) Kinematic differences between limbs will decrease over time because of changes in both ACL-reconstructed and ACL-intact limbs.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  In vivo kinematics of ACL-reconstructed and contralateral ACL-intact knees were evaluated for 14 subjects during single-legged forward-hop landings at 5 and 12 months after surgery on the basis of dynamic stereo x-ray imaging. Differences between limbs and changes over time were assessed via repeated-measures analysis of variance.
  
  
  RESULTS
  Five months after surgery, ACL-reconstructed knees landed significantly less flexed compared with contralateral ACL-intact knees (20.9° vs 28.4°, respectively; P < .05). The ACL-reconstructed knees were significantly more externally rotated (12.2° vs 6.5°; P < .05) and medially translated (3.8 vs 2.3 mm; P < .009) compared with ACL-intact knees. Anterior-posterior translation was similar between limbs. From 5 to 12 months, knee flexion at landing increased in ACL-reconstructed knees (mean change, +3.4°; P < .05) and decreased in contralateral knees (mean change, -3.3°; P < .05). External tibial rotation also significantly decreased in ACL-reconstructed knees (-2.2°; P < .05) and increased in contralateral knees (+1.1°; P = .117) over time. Medial tibial translation decreased slightly over time only in ACL-reconstructed knees (-0.3 mm).
  
  
  CONCLUSIONS
  Five months after ACL reconstruction, landing kinematics differed between ACL-reconstructed and contralateral ACL-intact knees during a dynamic high-loading activity. These differences decreased over time, owing to changes in both the ACL-reconstructed and contralateral ACL-intact limbs.
  
  
  CONCLUSIONS
  This study identified kinematic changes over time in both the ACL-injured and contralateral ACL-intact knees after ACL reconstruction. These kinematic adaptations could have important implications for postoperative care, including evaluating the optimal timing of return to sports and the development of bilateral neuromuscular rehabilitation programs that may improve patient outcomes and reduce reinjuries in both the short and long terms.
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA Department of Trauma Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Marcus
authors.initials: M
authors.lastname: Hofbauer
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Thorhauer
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Ermias
authors.initials: E
authors.lastname: Abebe
authors.affiliation: Bone and Joint Center, Henry Ford Health System, Detroit, Michigan, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Bey
authors.affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA tashman@pitt.edu.
authors.forename: Scott
authors.initials: S
authors.lastname: Tashman
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005080:Exercise Test; D005260:Female; D005269:Femur / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D013977:Tibia / Q000503:physiopathology*; D013997:Time Factors; D055815:Young Adult
keywords: ACL reconstruction; knee kinematics