Knee Injury and Osteoarthritis Outcome Score - Child

Original Editor - Michelle Lee

Top Contributors - Michelle Lee, Evan Thomas and Kim Jackson


The knee injury osteoarthritis score (KOOS) is an adult outcome measure used for assessing the patients' perspectives of their knee pain and disability. This tool was developed initially to use on adults. The KOOS pschometric properties have shown high reliability and validity, and is responsive to change in subjects with knee degeneration or knee injury.[1] 


Historically it was known that there were no specific paediatric outcome measures for knee pain, therefore the KOOS for adults was being used on children. It was not until 2012 when a group of researchers decided to look at the use of the adult KOOS with children.[2] They conducted cognitive interviews with 34 Swedish children between the ages of 10 and 16 years old. Cognitive interviewing has been found to be the gold standard methodology for assessing flaws in surveys due to lack of comprehension of the subjects. [3][4][5]

It was highlighted form this study that children who had undergone knee surgery or physiotherapy had a greater understanding of the medical terminology than those who had not. As such. they had a better comprehension of the KOOS for adults. It was recommended that due to this lack of comprehension in those who were not familiar with the terminology or younger children that the KOOS would need to be modified for them. This study did not identify a cut-off age for which the KOOS adult should be used, but recommended that comprehension was limited in younger children.[6]

The development of the KOOS - Child has lead to 5 sections with 39 questions in total. These categories are split into:

  • Knee problems
  • How painful
  • Difficulty during daily activities
  • Difficulty during sport and playing
  • How has your injury affected your life

Within these categories there are:

  • 7 questions on symptoms
  • 8 questions on pain
  • 11 questions on activities 
  • 7 questions on sports and play, and 
  • 6 questions on quality of life 

Psychometric Properties[7]

After the development of the KOOS - Child, the psychometric properties were evaluated in 2014. This study looked at children who were seeking medical attention for knee symptoms between the ages of 7-16 years old.[6] These authors attempted to evaluate:

  • Construct validity - All of the hypothesis were confirmed therefore this indicated that there was excellent construct validity.
  • Test-retest reliability - found that all test-retest's were excellent for all sub-scale except the symptoms scale which was slightly lower reliability.
  • Responsiveness - a hypothesis of a correlation of ≥ 0.3 between the KOOS Child sub-scale scores and the Global Perceived Effect (GPE) was confirmed therefore confirming the responsiveness of the KOOS Child.
  • Interperability - there were no floor to ceiling effects found. Minimal important changes (MIC) were found to complement the 95% Confidence Intervals (CI), and the MIC were better than the smallest detectable change (SDC)  for subjects who reported they were 'better' and 'much better'

Overall, the KOOS-Child shows excellent psychometric properties in all areas except internal consistency where the category 'symptoms' showed lower homogeneity, similar to the KOOS - Adult, and was thought to be due to patients being able to experience a wide variety of symptoms with knee conditions.


Unlike the KOOS - Adult where certain conditions are recommended for its use, the KOOS - Child can be used in a broad population of children with different knee disorders.[6] This page on paediatric knee disorders explorers different pathologies in which it may be used.


Each question has 5 possible answers, with each score ranging from 0-4. The least severe answer is scored as a 0, with the most severe being scored as a 4. For example:

  1. During the past month, how often have you experienced knee pain?
    • Never = 0
    • Rarely = 1
    • Sometimes = 2
    • Often = 3
    • Always = 4

Calculating the Score

Each subcategory is then added together. For example, all questions relating to pain are numbered P1, P2, P3, all questions relating to symptoms are numbered S1, S2, S3, etc.

The following is the manual calculation. This resultant score is the KOOS-Child subscale estimate for that particular cross-sectional assessment of the individual patient:

KOOS Child calc.png
Alternatively there is an excel spreadsheet which is downloadable from this website. The files name is the updated scoring file.



  1. Roos E M, Roos H P, Ekdahl C, Lohmander L S. Knee injury and Osteoarthritis Outcome Score (KOOS)—validation of a Swedish version. Scandinavian Journal of Medical Science and Sports 1998; 8:439-48.
  2. Örtqvist M1, Roos EM, Broström EW, Janarv PM, Iversen MD. Development of the Knee Injury and Osteoarthritis Outcome Score for children (KOOS-Child):Comprehensibility and content validity. Acta Orthopaedica 2012; 83(6): 666–673
  3. Willis G B, Royston P, Bercini D. The use of verbal report methods in the development and testing of survey questionnaires. Applied cognitive Psychology 1991; 5: 251-67.
  4. Willis G B. Cognitive interviewing: A tool for improving questionnaire design. Sage Publications, Thousand Oaks 2005
  5. Tourangeau R, Rips L J, Rasinski K. The psychology of survey response. Cambridge University Press, Cambridge 2002
  6. 6.0 6.1 6.2 Örtqvist M1, Roos EM, Broström EW, Janarv PM, Iversen MD. Development of the Knee Injury and Osteoarthritis Outcome Score for children (KOOS-Child):Comprehensibility and content validity. Acta Orthopaedica 2012; 83(6): 666–673
  7. Örtqvist M, Iversen MD, Janarv P-M, Broström EW, Roos EM. Psychometric properties of the Knee injury and Osteoarthritis Outcome Score for Children (KOOS-Child) in children with knee disorders. British Journal of Sports Medicine 2014; 48:1437–1446