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
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
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.
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
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
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
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