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Psychometric properties of the Knee injury and Osteoarthritis Outcome Score for Children (KOOS-Child) in children with knee disorders
  1. Maria Örtqvist1,
  2. Maura D Iversen1,2,3,4,
  3. Per-Mats Janarv1,
  4. Eva W Broström1,
  5. Ewa M Roos5
  1. 1Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden
  2. 2Section of Clinical Sciences, Division of Rheumatology, Immunology and Allergy, Brigham & Women's Hospital, Boston, Massachusetts, USA
  3. 3Harvard Medical School, Boston, Massachusetts, USA
  4. 4Department of Physical Therapy, Movement and Rehabilitation Sciences, Northeastern University, Boston, Massachusetts, USA
  5. 5Unit for Musculoskeletal Function and Physiotherapy, Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark
  1. Correspondence to Maria Örtqvist, Motion Analysis Laboratory Q2:07, Astrid Lindgren Children's Hospital, Stockholm S-171 76, Sweden; maria.ortqvist{at}ki.se

Abstract

Background The Knee injury and Osteoarthritis Outcome Score (KOOS) is a self-administered valid and reliable questionnaire for adults with joint injury or degenerative disease. Recent data indicate a lack of comprehensibility when this is used with children. Thus, a preliminary KOOS-Child was developed. This study aims to evaluate psychometric properties of the final KOOS-Child when used in children with knee disorders.

Methods 115 children (boys/girls 51/64, 7–16 years) with knee disorders were recruited. All children (n=115) completed the KOOS-Child, the Child-Health Assessment Questionnaire (CHAQ) and the EQ-5D-Youth version (EQ-5D-Y) at baseline to evaluate construct validity. Two additional administrations (1–3 weeks and 3 months) were performed for analyses of reliability (internal consistency and test–retest; n=72) and responsiveness (n=91). An anchor-based approach was used to evaluate responsiveness and interpretability.

Results After item reduction, the final KOOS-Child consists of 39 items divided into five subscales. No floor or ceiling effects (≤15%) were found. An exploratory factor analysis on subscale level demonstrated that items in all subscales except for Symptoms loaded on one factor (Eigenvalues 3.1–5.5, Symptom: 2 factors, Eigenvalue >1). Sufficient homogeneity was found for all subscales (Cronbach's α = 0.80–0.90) except for the Symptoms subscale (α = 0.59). Test–retest reliability was substantial to excellent for all subscales (Intraclass Correlation Coefficient 0.78–0.91, Smallest Detectable Change (SDC)ind 14.6–22.6, SDCgroup 1.7–2.7). Construct validity was confirmed, and greater effect sizes were seen in those reporting improved clinical status. Minimal important changes greater than the SDCs were found for patients reporting to be better and much better.

Conclusions The final KOOS-Child demonstrates good psychometric properties and supports the use of the KOOS-Child when evaluating children with knee disorders.

  • Knee Injuries
  • Physiotherapy
  • Children
  • Evaluation
  • Orthopaedics

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