title: Knee joint contact mechanics during downhill gait and its relationship with varus/valgus motion and muscle strength in patients with knee osteoarthritis.
abstract: OBJECTIVE
  The objective of this exploratory study was to evaluate tibiofemoral joint contact point excursions and velocities during downhill gait and assess the relationship between tibiofemoral joint contact mechanics with frontal-plane knee joint motion and lower extremity muscle weakness in patients with knee osteoarthritis (OA).
  
  
  METHODS
  Dynamic stereo X-ray was used to quantify tibiofemoral joint contact mechanics and frontal-plane motion during the loading response phase of downhill gait in 11 patients with knee OA and 11 control volunteers. Quantitative testing of the quadriceps and the hip abductor muscles was also performed.
  
  
  RESULTS
  Patients with knee OA demonstrated larger medial/lateral joint contact point excursions (p < 0.02) and greater heel-strike joint contact point velocities (p < 0.05) for the medial and lateral compartments compared to the control group. The peak medial/lateral joint contact point velocity of the medial compartment was also greater for patients with knee OA compared to their control counterparts (p = 0.02). Additionally, patients with knee OA demonstrated significantly increased frontal-plane varus motion excursions (p < 0.01) and greater quadriceps and hip abductor muscle weakness (p = 0.03). In general, increased joint contact point excursions and velocities in patients with knee OA were linearly associated with greater frontal-plane varus motion excursions (p < 0.04) but not with quadriceps or hip abductor strength.
  
  
  CONCLUSIONS
  Altered contact mechanics in patients with knee OA may be related to compromised frontal-plane joint stability but not with deficits in muscle strength.
authors.affiliation: Human Movement Research Laboratory, University of Pittsburgh, Pittsburgh, PA, USA. Farrokhi@pitt.edu
authors.forename: Shawn
authors.initials: S
authors.lastname: Farrokhi
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Voycheck
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Gustafson
authors.forename: G Kelley
authors.initials: GK
authors.lastname: Fitzgerald
authors.forename: Scott
authors.initials: S
authors.lastname: Tashman
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000503:physiopathology*; D016059:Range of Motion, Articular / Q000502:physiology*
keywords: Contact mechanics; Hip abductors; Instability; Kinematics; Quadriceps