The Oxford Knee Score; problems and pitfalls.

The Oxford Knee Score is a self-completed patient based outcome score. We audited the outcome of total knee arthroplasty at our unit using the Oxford Knee Score. The hypothesis of this study is that the OKS can be easily and accurately completed by unassisted patients. Of 856 patients who had undergone total knee arthroplasty and were given questionnaires, 769 (90%) responded. 624 (81%) of the respondents managed to complete the questionnaire. A number of the 12 items composing the questionnaire posed problems for the patients and a number of items were left blank. Item 4 (concerning walking time) was omitted in 82 (13%) of the 624 completed questionnaires. Calculation of Cronbach's alpha for internal consistency suggests that there are redundancies within the Score. Limitations in some of the items of the scale suggest the need for reconsideration and reformulation of questions and response categories. This study suggests that where detailed assessment of outcome is required, such as for outcome studies or controlled trials, the Oxford Knee Score, in its present form, is not ideal for use as a postal questionnaire.