Oxford Knee Score (OKS)

The Oxford Knee Score was developed and published in 1998 in order to expand the assessment spectrum of patients after total knee arthroplasty (TKA). At the time, evaluation was mainly done on the basis of clinical and radiological data. So, the OKS was intended to help take into account the patient’s individual assessment.1

Content

The Oxford Knee Score is a Patient Reported Outcome Measure (PROM), consisting  of 12 questions and assesses the subscales “pain” and “physical function” of patients with TKA. In a development study, Dawson et al. interviewed outpatients before TKA identifying their experiences and expressions when describing their knee problems. Based on the results, the authors developed 20 questions, tested them on patients several times and revised them. Eventually, 12 questions were considered for the final Oxford Knee Score.1

  1. Pain – 5 questions
  2. Physical function – 7 questions
Oxford Knee Score 1
Score Evaluation

Originally, the evaluation of the Oxford Knee Score was as follows:

First, each of the 12 answers are  assigned the previously defined number of points. They range from 1 = least difficult to 5 = most difficult. The 12 ratings are then added together  to give a total score used to assess the patient. The possible total score ranges from 12 to 60 points. Here, a low score (e.g. 12 points) indicates good outcomes and vice versa.1 

Because of misunderstandings concerning this, the right holders proposed a different system where response points range from 0 to 4 with a total score range from 0 to 48. Here, a high score (e.g. 48) indicates satisfactory joint function and vice versa.

Both scoring systems remain valid. To avoid misinterpretation one should always show the scoring system used. 

Strengths

The Oxford Knee Score is an established and validated score that is easy to implement and widely used in clinical research and patient care due to its comparatively small size. This is a significant advantage over other more comprehensive questionnaires such as the WOMAC Osteoarthritis Index. Furthermore, the rate of patients able to complete the questionnaire was higher than most other common health questionnaires, so that the likelihood of having augmented data is greater.1-6

Limitations

A study showed that the Oxford Knee Score has a low specificity. Thus, patients with healthy knees but other joint problems, such as complications in the hip or spine, would also score higher in the Oxford Knee Score.7

License

Using the Oxford Knee Score requires licensing by the copyright holder. It is free of charge for non-commercial users, but fees are charged for accompanying materials. Commercial users, large private practices and users whose projects are funded by the industry have to pay royalties.8,9

Conclusion

Overall, the Oxford Knee Score, as an established and validated score suitable instrument for everyday clinical use, particularly because of its significance and small size. Due to its low specificity however, one should take into account that the score could be falsified by joint problems in adjacent body areas.7

SOURCES:

  1. Dawson J, Fitzpatrick R, Murray D, Carr A. Questionnaire on the perceptions of patients about total knee replacement. J Bone Joint Surg Br 1998;80:63-9.
  2. Garratt AM, Brealey S, Gillespie WJ, Team DT. Patient-assessed health instruments for the knee: a structured review. Rheumatology (Oxford) 2004;43:1414-23.
  3. Benson T, Williams DH, Potts HW. Performance of EQ-5D, howRu and Oxford hip & knee scores in assessing the outcome of hip and knee replacements. BMC Health Serv Res 2016;16:512.
  4. Harris KK, Dawson J, Jones LD, Beard DJ, Price AJ. Extending the use of PROMs in the NHS–using the Oxford Knee Score in patients undergoing non-operative management for knee osteoarthritis: a validation study. BMJ Open 2013;3:e003365.
  5. Xie F, Ye H, Zhang Y, Liu X, Lei T, Li SC. Extension from inpatients to outpatients: validity and reliability of the Oxford Knee Score in measuring health outcomes in patients with knee osteoarthritis. Int J Rheum Dis 2011;14:206-10.
  6. Naal FD, Impellizzeri FM, Sieverding M, et al. The 12-item Oxford Knee Score: cross-cultural adaptation into German and assessment of its psychometric properties in patients with osteoarthritis of the knee. Osteoarthritis Cartilage 2009;17:49-52.
  7. Harcourt WG, White SH, Jones P. Specificity of the Oxford knee status questionnaire. The effect of disease of the hip or lumbar spine on patients‘ perception of knee disability. J Bone Joint Surg Br 2001;83:345-7.
  8. https://innovation.ox.ac.uk/outcome-measures/oxford-knee-score-oks/ (Accessed November 15th, 2019)
  9. https://process.innovation.ox.ac.uk/ (Accessed November 15th, 2019)