title: A novel experimental knee-pain model affects perceived pain and movement biomechanics.
abstract: BACKGROUND
  Knee injuries are prevalent, and the associated knee pain is linked to disability. The influence of knee pain on movement biomechanics, independent of other factors related to knee injuries, is difficult to study and unclear.
  
  
  OBJECTIVE
  (1) To evaluate a novel experimental knee-pain model and (2) better understand the independent effects of knee pain on walking and running biomechanics.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  Biomechanics laboratory.
  
  
  METHODS
  Twelve able-bodied volunteers (age = 23 ± 3 years, height = 1.73 ± 0.09 m, mass = 75 ± 14 kg).
  
  
  METHODS
  Participants walked and ran at 3 time intervals (preinfusion, infusion, and postinfusion) for 3 experimental conditions (control, sham, and pain). During the infusion time interval for the pain and sham conditions, hypertonic or isotonic saline, respectively, was continuously infused into the right infrapatellar fat pad for 22 minutes.
  
  
  METHODS
  We used repeated-measures analyses of variance to evaluate the effects of time and condition on (1) perceived knee pain and (2) key biomechanical characteristics (ground reaction forces, and joint kinematics and kinetics) of walking and running (P < .05).
  
  
  RESULTS
  The hypertonic saline infusion (1) increased perceived knee pain throughout the infusion and (2) reduced discrete characteristics of each component of the walking ground reaction force, walking peak plantar-flexion angle (range = 62°-67°), walking peak plantar-flexion moment (range = 95-104 N·m), walking peak knee-extension moment (range = 36-49 N·m), walking peak hip-abduction moment (range = 62-73 N·m), walking peak support moment (range = 178-207 N·m), running peak plantar-flexion angle (range = 38°-77°), and running peak hip-adduction angle (range = 5-21°).
  
  
  CONCLUSIONS
  This novel experimental knee pain model consistently increased perceived pain during various human movements and produced altered running and walking biomechanics that may cause abnormal knee joint-loading patterns.
authors.affiliation: Brigham Young University, Provo, UT 84602, USA. matt_seeley@byu.edu
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Seeley
authors.forename: Jihong
authors.initials: J
authors.lastname: Park
authors.forename: Daniel
authors.initials: D
authors.lastname: King
authors.forename: J Ty
authors.initials: JT
authors.lastname: Hopkins
mesh_terms: D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D010147:Pain Measurement; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D012420:Running / Q000502:physiology; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage; D016138:Walking / Q000502:physiology; D055815:Young Adult
chemical_list: D012462:Saline Solution, Hypertonic