title: Early Changes in Knee Center of Rotation During Walking After Anterior Cruciate Ligament Reconstruction Correlate With Later Changes in Patient-Reported Outcomes.
abstract: BACKGROUND
  Altered knee kinematics after anterior cruciate ligament injury and reconstruction (ACLR) have been implicated in the development of posttraumatic osteoarthritis (PTOA), leading to poor long-term clinical outcomes.
  
  
  OBJECTIVE
  This study was conducted to determine (1) whether the average knee center of rotation (KCOR), a multidimensional metric of knee kinematics, of the ACL-reconstructed knee during walking differs from that of the uninjured contralateral knee; (2) whether KCOR changes between 2 and 4 years after surgery; and (3) whether early KCOR changes predict patient-reported outcomes 8 years after ACLR.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Twenty-six human participants underwent gait analysis with calculation of bilateral KCOR during walking at 2 and 4 years after unilateral ACLR. Knee injury and Osteoarthritis Outcome Score (KOOS) and Lysholm score results were collected at 2, 4, and 8 years after ACLR in 13 of these participants.
  
  
  RESULTS
  The ACL-reconstructed knee showed greater medial compartment motion because of pivoting about a more lateral KCOR ( P = .03) than the contralateral knee at 2 years. KCOR became less lateral over time ( P = .047), with values approaching those of the uninjured knee by 4 years ( P = .55). KCOR was also more anterior in the ACL-reconstructed knee at 2 years ( P = .02). Between 2 and 4 years, KCOR moved posteriorly in 16 (62%) and anteriorly in 10 (38%) participants. Increasing the anterior position of KCOR in the ACL-reconstructed knee from 2 to 4 years correlated with worsening clinical outcomes at 4 years (KOOS-Quality of Life, R2= 0.172) and more strongly at 8 years (Lysholm score, R2= 0.41; KOOS-Pain, R2= 0.37; KOOS-Symptoms, R2= 0.58; and KOOS-Quality of Life, R2= 0.50).
  
  
  CONCLUSIONS
  The observed changes to KCOR during walking between 2 and 4 years after ACLR show progressive improvement toward kinematic symmetry over the 2-year follow-up. The correlation between increasingly abnormal kinematics and worsening clinical outcomes years later in a subset of participants provides a potential explanation for the incidence of PTOA after ACLR.
authors.affiliation: Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA.|Veterans Affairs Palo Alto, Palo Alto, California, USA.|BioMotion Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Titchenal
authors.affiliation: Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA.|Veterans Affairs Palo Alto, Palo Alto, California, USA.
authors.forename: Constance R
authors.initials: CR
authors.lastname: Chu
authors.affiliation: Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA.|Veterans Affairs Palo Alto, Palo Alto, California, USA.|BioMotion Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Erhart-Hledik
authors.affiliation: Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California, USA.|Veterans Affairs Palo Alto, Palo Alto, California, USA.|BioMotion Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, California, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Andriacchi
mesh_terms: D000328:Adult; D000070598:Anterior Cruciate Ligament Injuries / Q000503:physiopathology* / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D007717:Knee / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D020370:Osteoarthritis, Knee / Q000209:etiology; D010146:Pain / Q000503:physiopathology; D000071066:Patient Reported Outcome Measures; D011788:Quality of Life; D012399:Rotation; D016138:Walking / Q000502:physiology*
keywords: ACL reconstruction; center of rotation; gait analysis; knee kinematics; osteoarthritis; patient-reported outcomes