title: The effect of knee extensor open kinetic chain resistance training in the ACL-injured knee.
abstract: OBJECTIVE
  To investigate the effect of different loads of knee extensor open kinetic chain resistance training on anterior knee laxity and function in the ACL-injured (ACLI) knee.
  
  
  METHODS
  Fifty-eight ACLI subjects were randomised to one of three (12-week duration) training groups. The STAND group trained according to a standardised rehabilitation protocol. Subjects in the LOW and HIGH group trained as did the STAND group but with the addition of seated knee extensor open kinetic chain resistance training at loads of 2 sets of 20 repetition maximum (RM) and 20 sets of 2RM, respectively. Anterior knee laxity and measurements of physical and subjective function were performed at baseline, 6 and 12 weeks. Thirty-six subjects were tested at both baseline and 12 weeks (STAND n = 13, LOW n = 11, HIGH n = 12).
  
  
  RESULTS
  The LOW group demonstrated a reduction in 133 N anterior knee laxity between baseline and 12 weeks testing when compared to the HIGH and the STAND groups (p = 0.009). Specifically, the trained-untrained knee laxity decreased an average of approximately 5 mm in the LOW group while remaining the same in the other two groups.
  
  
  CONCLUSIONS
  Twelve weeks of knee extensor open kinetic chain resistance training at loads of 2 sets of 20RM led to a reduction in anterior knee laxity in the ACLI knee. This reduction in laxity does not appear to offer any significant short-term functional advantages when compared to a standard rehabilitation protocol. These results indicate that knee laxity can be decreased with resistance training of the thigh muscles.
  
  
  METHODS
  Randomised controlled trial, Level II.
authors.affiliation: Academic Department of Physiotherapy, School of Medicine, King's College London, London, UK.
authors.forename: Massimo G
authors.initials: MG
authors.lastname: Barcellona
authors.affiliation: Faculty of Health Sciences, University of Ljubljana, Ljubljana, Slovenia. morrissey.matt@ymail.com.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Morrissey
authors.affiliation: King's College London, London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Milligan
authors.affiliation: Guy's and St. Thomas' Hospital, London, UK.
authors.forename: Melissa
authors.initials: M
authors.lastname: Clinton
authors.affiliation: Department of Mechanical Engineering, Imperial College London, London, UK.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Amis
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000534:rehabilitation*; D007700:Kinetics; D007718:Knee Injuries / Q000503:physiopathology / Q000534:rehabilitation*; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology; D055070:Resistance Training / Q000379:methods*; D055815:Young Adult
keywords: Hypermobility; Joint stability; Quadriceps; Resistance training; Therapeutic exercise