The Knee injury and Osteoarthritis Outcome Score, Junior (KOOS JR.) is a new outcome reporting tool, validated in 2015.

KOOS JR. has received a lot of interest from the orthopedic community as an efficient and reliable alternative to the longer Knee injury Osteoarthritis Outcome Score (KOOS) reporting tool. The widely used KOOS questionnaire measures joint-specific pain, physical function, and contains 42 questions. The KOOS JR. has just seven.

The questions in the KOOS JR. are taken directly from its parent questionnaire and focus on the three categories: joint pain, stiffness and function in daily living.  By comparison, KOOS focuses on five categories: pain, function in daily living, function in sport and recreation, other symptoms, and knee-related quality of life. The brevity of KOOS JR. allows for faster completion and greater patient engagement.

What PRO tools are available for TKA patients?

We break them down in our Knee PRO Tools Guide. Download Now.


The main advantage of KOOS JR. is its significantly shortened length. With a completion time of under 3 minutes, it’s an attractive alternative to the much longer KOOS.

The HSS validation cohort and the FORCE-TJR registry have both validated KOOS JR. Its internal consistency was found to be high, and research suggested that there was near-perfect correlation with both the pain and activities of daily living/function domains of the full KOOS survey and the WOMAC reporting tool (Spearman’s correlations 0.80-0.94). Additionally, as a validated tool KOOS JR. score can be derived from the longer KOOS survey.

Another advantage of the KOOS JR. is that its scoring methodology is easier to apply than that of the KOOS tool. In the new tool, patients rate each activity by indicating the amount of pain or disability they experience while carrying them out. Raw scores are added up (range 0-28) and converted to an interval score (0-100) using the appropriate table. The interval score represents a patients total joint disability where 0 corresponds to total joint disability and 100 perfect joint health.



As a newly validated outcome tool there is very little literature at present about KOOS JR. Further studies and research should help provide a more complete picture about the robustness, reliability and viability of the KOOS JR. as outcome reporting tools.



No license is needed to use KOOS JR and can be obtained free of charge here.

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  1. The joint commission: Candidate Performance Measure Profile –
  2. Patient Reported Outcomes Summit for Total Joint Arthroplasty Report. August 2015 –
  3. Joint Communication from the American Association of Orthopaedic Surgeons, the American joint replacement registry, The Hip Society, The Knee Society, and the American Association of Hip and Knee Surgeons. Issued 8 September 2015. –
  4. Roos, E. M., & Lohmander, L. S. (2003). The Knee injury and Osteoarthritis Outcome Score (KOOS): from joint injury to osteoarthritis. Health and Quality of Life Outcomes, 1, 64. –
  5. Peer MA, Lane J. J Orthop Sports Phys Ther. 2013 Jan;43(1):20-8. doi: 10.2519/jospt.2013.4057. Epub 2012 Dec 7. Review. –
  6. Davis, A. M., Perruccio, A. V., Canizares, M., Hawker, G. A., Roos, E. M., Maillefert, J. F., & Lohmander, L. S. (2009). Comparative, validity and responsiveness of the HOOS-PS and KOOS-PS to the WOMAC physical function subscale in total joint replacement for osteoarthritis. Osteoarthritis and Cartilage, 17(7), 843-847. –