title: Knee contact forces are not altered in early knee osteoarthritis.
abstract: OBJECTIVE
  This study calculated knee contact forces (KCF) and its relations with knee external knee adduction moments (KAM) and/or flexion moments (KFM) during the stance phase of gait in patients with early osteoarthritis (OA), classified based on early joint degeneration on Magnetic Resonance Imaging (MRI). We aimed at assessing if altered KCF are already present in early structural degeneration.
  
  
  METHODS
  Three-dimensional motion and ground reaction force data in 59 subjects with medial compartment knee OA (N=23 established OA, N=16 early OA, N=20 controls) were used as input for a musculoskeletal model. KAM and KFM, and KCF were estimated using OpenSim software.
  
  
  RESULTS
  No significant differences were found between controls and subjects with early OA. In early OA patients, KAM significantly explained 69% of the variance associated with the first peaks KCF but only KFM contributed to the second peaks KCF. The multiple correlation, combining KAM and KFM, showed to be higher. However, only 20% of the variance of second peak KCF was explained by both moments in established OA.
  
  
  CONCLUSIONS
  KCF are not increased in patients with early OA, suggesting that knee joint overload is more a consequence of further joint degeneration in more advanced stages of OA. Additionally, our results clearly show that KAM is not sufficient to predict joint loading at the end of the stance, where KFM contributes substantially to the loading, especially in early OA.
authors.affiliation: Department of Kinesiology, KU Leuven, Belgium. Electronic address: susana.meireles@faber.kuleuven.be.
authors.forename: S
authors.initials: S
authors.lastname: Meireles
authors.affiliation: Department of Mechanical Engineering, KU Leuven, Belgium. Electronic address: Friedl.DeGroote@mech.kuleuven.be.
authors.forename: F
authors.initials: F
authors.lastname: De Groote
authors.affiliation: School of Healthcare Science, Manchester Metropolitan University, United Kingdom. Electronic address: N.Reeves@mmu.ac.uk.
authors.forename: N D
authors.initials: ND
authors.lastname: Reeves
authors.affiliation: Department of Rehabilitation Sciences, KU Leuven, Belgium. Electronic address: Sabine.Verschueren@faber.kuleuven.be.
authors.forename: S
authors.initials: S
authors.lastname: Verschueren
authors.affiliation: School of Sport and Exercise Sciences, Liverpool John Moores University, United Kingdom. Electronic address: c.maganaris@ljmu.ac.uk.
authors.forename: C
authors.initials: C
authors.lastname: Maganaris
authors.affiliation: Department of Development and Regeneration, KU Leuven, Belgium. Electronic address: frank.luyten@uz.kuleuven.ac.be.
authors.forename: F
authors.initials: F
authors.lastname: Luyten
authors.affiliation: Department of Kinesiology, KU Leuven, Belgium. Electronic address: ilse.jonkers@faber.kuleuven.be.
authors.forename: I
authors.initials: I
authors.lastname: Jonkers
mesh_terms: D000368:Aged; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology*; D011312:Pressure; D016059:Range of Motion, Articular / Q000502:physiology*; D013997:Time Factors; D016138:Walking / Q000502:physiology*
keywords: Gait; Knee contact forces; Knee osteoarthritis; Musculoskeletal model