title: Excellent balance skills despite active and inactive juvenile idiopathic arthritis - unexpected results of a cross-sectional study.
abstract: OBJECTIVE
  Postural control (PC) is fundamental for human movements. Different factors, such as injuries or diseases, can adversely affect PC. The purpose of this study was to evaluate PC in juvenile idiopathic arthritis (JIA) patients with different disease activity levels in comparison to healthy peers.
  
  
  METHODS
  JIA patients with active and inactive lower limb joints (n=36 each group) were examined. Both groups have been on medication and have had physiotherapy for at least 5 years. For comparison, an age- and gender-matched healthy control group (CG; n=36) participated. PC was measured bipedal on a balance-board (S3-Check, TST, Großhoeflein), with an instable tilting between left and right. The parameters of interest were the best results of Stability Index (STI), Sensorimotor Index (SMI) and Symmetry Index (SYI) out of 4 test trials as well as JIA disease-related variables. Data were analysed with descriptive statistics, comparison of averages, linear regression and correlations (p<0.05).
  
  
  RESULTS
  The three groups showed no differences in anthropometric characteristics and SYI (p>0.05). In both JIA groups, STI and SMI were lower than indices of CG (p<0.05), indicating better stability and motor control. Balance indices did not differ between active and inactive JIA patients (p>0.05).
  
  
  CONCLUSIONS
  JIA patients showed better PC than CG. Possible explanations are an increased body-awareness due to long-term physiotherapy and daily coordination training due to compensatory movements. The positive results highlight the success of individual, interdisciplinary treatment in JIA and can be used to promote recommendations for safe sport participation.
authors.affiliation: Department of Biomechanics in Sports, Faculty of Sports and Health Sciences, Technical University of Munich; and German Center for Paediatric and Adolescent Rheumatology, Garmisch-Partenkirchen, Germany. josephine.merker@tum.de.
authors.forename: Josephine
authors.initials: J
authors.lastname: Merker
authors.affiliation: German Center for Paediatric and Adolescent Rheumatology, Garmisch-Partenkirchen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hartmann
authors.affiliation: Department of Biomechanics in Sports, Faculty of Sports and Health Sciences, Technical University of Munich, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Kreuzpointner
authors.affiliation: Department of Biomechanics in Sports, Faculty of Sports and Health Sciences, Technical University of Munich, Germany.
authors.forename: Ansgar
authors.initials: A
authors.lastname: Schwirtz
authors.affiliation: German Center for Paediatric and Adolescent Rheumatology, Garmisch-Partenkirchen, Germany.
authors.forename: Johannes-Peter
authors.initials: JP
authors.lastname: Haas
mesh_terms: D000293:Adolescent; D001171:Arthritis, Juvenile / Q000503:physiopathology*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D012720:Severity of Illness Index