title: Gait changes in patients with knee osteoarthritis are replicated by experimental knee pain.
abstract: OBJECTIVE
  Medial knee osteoarthritis (OA) is characterized by pain and associated with abnormal knee moments during walking. The relationship between knee OA pain and gait changes remains to be clarified, and a better understanding of this link could advance the treatment and prevention of disease progression. This study investigated changes in knee moments during walking following experimental knee pain in healthy volunteers, and whether these changes replicated the joint moments observed in medial knee OA patients.
  
  
  METHODS
  In a crossover study, 34 healthy subjects were tested on 3 different days; gait analyses were conducted before, during, and after pain induced by hypertonic saline injections (0.75 ml) into the infrapatellar fat pad. Isotonic saline and sham injections were used as control conditions. Peak moments in frontal and sagittal planes were analyzed. The results were compared with data from 161 medial knee OA patients. The patients were divided into less severe OA and severe OA categories, which was based on radiographic disease severity of the medial compartment.
  
  
  RESULTS
  Experimental knee pain led to reduced peak moments in the frontal and sagittal planes in the healthy subjects, which were similar to the patterns observed in less severe OA patients while walking at the same speed.
  
  
  CONCLUSIONS
  In healthy subjects, pain was associated with reductions in knee joint moments during walking in a manner similar to less severe knee OA patients. The experimental model may be used to study mechanically-driven knee OA progression and preventive measures against abnormal joint loading in knee OA.
authors.affiliation: Clinical Motor Function Laboratory, Frederiksberg Hospital, Ndr. Fasanvej 57, Frederiksberg, Denmark. marius.henriksen@frh.regionh.dk
authors.forename: Marius
authors.initials: M
authors.lastname: Henriksen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
authors.forename: Jens
authors.initials: J
authors.lastname: Aaboe
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Andriacchi
authors.forename: Henning
authors.initials: H
authors.lastname: Bliddal
mesh_terms: D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D018592:Cross-Over Studies; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology*; D010146:Pain / Q000150:complications*; D010147:Pain Measurement; D011859:Radiography; D011897:Random Allocation; D016059:Range of Motion, Articular; D012720:Severity of Illness Index; D055815:Young Adult