The Oxford Knee Score (OKS)

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The Oxford Knee Score (OKS) is a 12-item patient-reported PRO specifically designed and developed to assess function and pain after total knee replacement (TKR) surgery (arthroplasty). It is short, reproducible, valid and sensitive to clinically important changes.


The OKS was designed to be completed by the patient thus minimising potential bias unwittingly introduced by surgeons when assessing the results themselves.

The PRO was designed and developed by researchers within Public Health and Primary Health Care at the University of Oxford in association with surgical colleagues at the Nuffield Orthopaedic Centre.

Some of the attributes of the Oxford Knee Score are:

  • a simple scoring system provides an overall scale for assessing outcomes of knee interventions
  • the PRO is completed by the patient, independent of the clinical team/surgeon
  • the PRO can be completed anywhere, can be delivered by post to patients’ homes or deployed by various electronic platforms such as web or PDA. This makes follow-up of large study populations much more feasible (and cheaper) than conducting clinical assessments, requiring a return visit to the hospital
  • It eliminates interobserver error
  • Users have reported extremely good response rates – 98% (Medalla 2009)
  • In large scale studies the OKS has been ranked the best disease/site-specific PRO for assessing outcome of knee arthroplasty (Dunbar 2001)


The OKS is a patient self-completion PRO containing 12 questions on activities of daily living. The OKS has been developed and validated specifically to assess function and pain after TKR.

Example studies

The OKS was primarily use to assess outcomes of TKR surgery. The use of the OKS has steadily increased and is now widely employed in many different types of studies including cohort studies, audits and in national joint replacement registries. Other examples of uses of the OKS include:

  • Assessment of patient outcomes following alternative non-surgical interventions, including physical therapy, joint supplements and anti-inflammatory medications
  • The Oxford Knee Score and the Oxford Hip Score (OHS) have recently been adopted by the UK Department of Health (DoH) for the assessment of approximately 120,000 hip and knee operations which are carried out each year in National Health Service (NHS) hospitals. The OHS and OKS form part of the nationwide Patient Reported Outcome Measure program launched by the UK DoH.
  • Private healthcare providers have also been interested in using the Oxford orthopaedic scores, including the OKS, to develop care pathways that achieve the best possible results for the patients. Nuffield Health (UK) is just one of our user community to obtain benefit from the OKS in this way.
  • Public and private healthcare providers have used the OKS to assess patient outcomes across multiple facilities as a measure of the performance of individual treatment centres, which can be used to identify high-performing centres and to raise standards through sharing best practices.

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Similar to the situation with hip replacement, prior to the development of the OKS, only crude measures of surgical failure such as the need to perform revision surgery had been employed in the assessment of patient outcomes. The development of the OKS was driven by the need to conduct more systematic and accurate monitoring of patient outcomes following TKR. As a relatively short instrument the OKS is particularly appropriate for use by older individuals who most often receive TKR.

Details of the development protocol and scoring system for the OKS are described in:

Dawson J, Fitzpatrick R, Carr A, Murray D. Questionnaire on the perceptions of patients about total hip replacement J Bone Joint Surg Br. 1998 Jan;80(1):63-69

Formats available:


Paper – Telephone administered version

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Scoring system

The OKS provides a single summed score which reflects the severity of problems that the respondent has with their knee. Details of the scoring system for the OKS can be downloaded in Useful Links section.

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Administration Methods

Pen and Paper ePRO/eCOA – Computer-based administration Telephone Interview

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Authorised eCOA vendors

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