title: Altered tibiofemoral joint contact mechanics and kinematics in patients with knee osteoarthritis and episodic complaints of joint instability.
abstract: BACKGROUND
  To evaluate knee joint contact mechanics and kinematics during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability.
  
  
  METHODS
  Forty-three subjects, 11 with medial compartment knee osteoarthritis and self-reported instability (unstable), 7 with medial compartment knee osteoarthritis but no reports of instability (stable), and 25 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a downhill gait task on a treadmill.
  
  
  RESULTS
  The medial compartment contact point excursions were longer in the unstable group compared to the stable (P=0.046) and the control groups (P=0.016). The peak medial compartment contact point velocity was also greater for the unstable group compared to the stable (P=0.047) and control groups (P=0.022). Additionally, the unstable group demonstrated a coupled movement pattern of knee extension and external rotation after heel contact which was different than the coupled motion of knee flexion and internal rotation demonstrated by stable and control groups.
  
  
  CONCLUSIONS
  Our findings suggest that knee joint contact mechanics and kinematics are altered during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. The observed longer medial compartment contact point excursions and higher velocities represent objective signs of mechanical instability that may place the arthritic knee joint at increased risk for disease progression. Further research is indicated to explore the clinical relevance of altered contact mechanics and kinematics during other common daily activities and to assess the efficacy of rehabilitation programs to improve altered joint biomechanics in knee osteoarthritis patients with self-reported instability.
authors.affiliation: Human Movement Research Laboratory, Departments of Physical Therapy & Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA. Electronic address: Farrokhi@pitt.edu.
authors.forename: Shawn
authors.initials: S
authors.lastname: Farrokhi
authors.affiliation: Department of Physical Therapy, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Voycheck
authors.affiliation: Orthopaedic Surgery, Department of Orthopaedic Surgery, University of Pittsburgh, PA, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Klatt
authors.affiliation: Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Gustafson
authors.affiliation: Biodynamics Laboratory, Department of Orthopaedic Surgery, Department of Bioengineering, University of Pittsburgh, PA, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Tashman
authors.affiliation: Department of Physical Therapy, Physical Therapy Clinical and Translational Research Center, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: G Kelley
authors.initials: GK
authors.lastname: Fitzgerald
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D015992:Body Mass Index; D016022:Case-Control Studies; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D012399:Rotation
keywords: Contact mechanics; Gait; Instability; Kinematics