Knee Injury and Osteoarthritis Outcome Score (KOOS)

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Originally published in 1998 in The Journal of Orthopaedic and Sports Physical Therapy, the Knee injury and Osteoarthritis Outcome Score (KOOS) assesses patient pain (9 items), other symptoms (7 items), function in daily living (17 items), function in sport and recreation (5 items), and knee related quality of life (4 items). Scores range from 0 to 100 with a score of 0 indicating the worst possible knee symptoms and 100 indicating no knee symptoms. The KOOS is a patient reported joint-specific score, which may be useful for assessing changes in knee pathology over time, with or without treatment.

Use the following EVALUATION FORM to evaluate your patient and PRINT THE FORM when the evaluation is completed.

Strengths and Limitations


The KOOS score is a validated and established patient-reported outcome instrument that is commonly used in clinical research as well as inpatient care.

However, its major strength is that it captures not only the short-term effects of knee injuries but also their important long-term consequences, namely post-traumatic osteoarthritis. The inclusion of the WOMAC PROM within it lends KOOS this benefit and so scores relating to long-term pain, stiffness, and function of the knee in the elderly population can be derived from it which can be informative when prescribing medications/evaluating the benefit of additional interventions.


Comprising of 42 questions, the KOOS is regarded as being a long PROM to complete. Patients take an estimated 8 minutes to complete a KOOS questionnaire, which requires good time management or ideally electronic data collection in inpatient care settings. This factor can also hinder patient engagement with this PROM, thus affecting response rates.


Original Literature:

  • Roos, Ewa M., et al. “Knee Injury and Osteoarthritis Outcome Score (KOOS)—development of a self-administered outcome measure.” Journal of Orthopaedic & Sports Physical Therapy 28.2 (1998): 88-96.

Additional Literature:

  • Roos, Ewa M., and Sören Toksvig-Larsen. “Knee injury and Osteoarthritis Outcome Score (KOOS)–validation and comparison to the WOMAC in total knee replacement.” Health and quality of life outcomes 1.1 (2003): 17.
  • Wang, Dean, et al. “Patient-reported outcome measures for the knee.” The journal of knee surgery 23.03 (2010): 137-151.
  • Vaquero, Javier, et al. “Reliability, validity and responsiveness of the Spanish version of the Knee Injury and Osteoarthritis Outcome Score (KOOS) in patients with chondral lesion of the knee.” Knee Surgery, Sports Traumatology, Arthroscopy 22.1 (2014): 104-108.

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