title: The impact of simulated ankle plantarflexion contracture on the knee joint during stance phase of gait: a within-subject study.
abstract: BACKGROUND
  Ankle plantarflexion contractures are common in adults with neurological disorders and known to cause secondary gait deviations. However, their impact on the knee joint is not fully understood. The aims of this study are to describe the effect of simulated plantarflexion contractures on knee biomechanics during the stance phase and on the spatiotemporal characteristics of gait.
  
  
  METHODS
  Mild (10-degree plantarflexion) and severe (20-degree plantarflexion) ankle contractures were simulated in thirteen able-bodied adults using an ankle-foot-orthosis. A no contracture condition was compared with two simulated contracture conditions.
  
  
  RESULTS
  There was an increase in knee extension, sometimes resulting in hyperextension, throughout stance for the two contracture conditions compared to the no contracture condition (mean increase in knee extension ranged from 5° to 9°; 95% CI 0° to 17°). At the same time, there were reductions in extension moment and power generation at the knee. Simulated plantarflexion contractures also reduced gait velocity, bilateral step length and cadence. All these changes were more pronounced in the severe contracture condition than mild contracture condition. While the majority of participants adopted a foot-flat pattern on landing and exhibited an increase in knee extension during stance, two participants used a toe-walking pattern and exhibited an increase in knee flexion.
  
  
  CONCLUSIONS
  Ankle plantarflexion contractures are associated with an increase in knee extension during stance phase. However, some people with simulated ankle contractures may walk with an increase in knee flexion instead. Ankle plantarflexion contractures also adversely affect gait velocity, step length and cadence.
authors: Brain Injury Unit, Royal Rehabilitation Centre Sydney, PO Box 6, Ryde, NSW 1680, Australia; John Walsh Centre for Rehabilitation Research, Sydney Medical School/Northern, Kolling Institute, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW 2065, Australia. Electronic address: joan.leung@royalrehab.com.au.
authors: Joan
authors: J
authors: Leung
authors: Exercise and Sport Science, Faculty of Health Sciences, University of Sydney, 75 East Street, Lidcombe, NSW 2141, Australia. Electronic address: richard.smith@sydney.edu.au.
authors: Richard
authors: R
authors: Smith
authors: John Walsh Centre for Rehabilitation Research, Sydney Medical School/Northern, Kolling Institute, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW 2065, Australia. Electronic address: l.harvey@usyd.edu.au.
authors: Lisa Anne
authors: LA
authors: Harvey
authors: The George Institute for Global Health, Level 13/321 Kent Street, Sydney, NSW 2000, Australia. Electronic address: amoseley@georgeinstitute.org.au.
authors: Anne M
authors: AM
authors: Moseley
authors: Premier Prosthetics and Orthotics Pty Ltd., Unit 52/2 Railway Parade, Lidcombe, NSW 2141, Australia.
authors: Joseph
authors: J
authors: Chapparo
mesh_terms: D000842:Ankle / Q000503:physiopathology*; D016512:Ankle Injuries / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D003286:Contracture / Q000503:physiopathology*; D005260:Female; D005684:Gait; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D016544:Patient Simulation; D016138:Walking
keywords: Ankle; Biomechanics; Cerebral palsy; Contracture; Knee; Stroke