title: Knee pain during strength training shortly following fast-track total knee arthroplasty: a cross-sectional study.
abstract: BACKGROUND
  Loading and contraction failure (muscular exhaustion) are strength training variables known to influence neural activation of the exercising muscle in healthy subjects, which may help reduce neural inhibition of the quadriceps muscle following total knee arthroplasty (TKA). It is unknown how these exercise variables influence knee pain after TKA.
  
  
  OBJECTIVE
  To investigate the effect of loading and contraction failure on knee pain during strength training, shortly following TKA.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Consecutive sample of patients from the Copenhagen area, Denmark, receiving a TKA, between November 2012 and April 2013.
  
  
  METHODS
  Seventeen patients, no more than 3 weeks after their TKA.
  
  
  METHODS
  In a randomized order, the patients performed 1 set of 4 standardized knee extensions, using relative loads of 8, 14, and 20 repetition maximum (RM), and ended with 1 single set to contraction failure (14 RM load). The individual loadings (kilograms) were determined during a familiarization session >72 hours prior. The patients rated their knee pain during each repetition, using a numerical rating scale (0-10).
  
  
  RESULTS
  Two patients were lost to follow up. Knee pain increased with increasing load (20 RM: 3.1±2.0 points, 14 RM: 3.5±1.8 points, 8 RM: 4.3±2.5 points, P = 0.006), and repetitions to contraction failure (10% failure: 3.2±1.9 points, 100% failure: 5.4±1.6 points, P<0.001). Resting knee pain 60 seconds after the final repetition (2.7±2.4 points) was not different from that recorded before strength training (2.7±1.8 points, P = 0.88).
  
  
  CONCLUSIONS
  Both loading and repetitions performed to contraction failure during knee- extension strength-training, increased post-operative knee pain during strength training implemented shortly following TKA. However, only the increase in pain during repetitions to contraction failure exceeded that defined as clinically relevant, and was very short-lived.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT01729520.
authors.affiliation: Physical Medicine & Rehabilitation Research - Copenhagen (PMR-C), Department of Physical Therapy, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Clinical Research Centre, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Department of Orthopedic Surgery, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bandholm
authors.affiliation: Physical Medicine & Rehabilitation Research - Copenhagen (PMR-C), Department of Physical Therapy, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Department of Orthopedic Surgery, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Arthroscopic Center Amager, Amager Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Thorborg
authors.affiliation: Department of Anaesthesiology, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Lundbeckfoundation Centre for Fast-track Hip and Knee Surgery, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Troels Haxholdt
authors.initials: TH
authors.lastname: Lunn
authors.affiliation: Lundbeckfoundation Centre for Fast-track Hip and Knee Surgery, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Section for Surgical Pathophysiology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Henrik
authors.initials: H
authors.lastname: Kehlet
authors.affiliation: Clinical Research Centre, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark; Lundbeckfoundation Centre for Fast-track Hip and Knee Surgery, Hvidovre Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas Linding
authors.initials: TL
authors.lastname: Jakobsen
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D010146:Pain / Q000503:physiopathology*; D055070:Resistance Training; D016474:Weight-Bearing