Oxford Knee Score (OKS). The OKS is a self-completed patient based outcome score . It is a 12 item self-completed patient based outcome score. The questionnaire was developed from patient interview and validated against two generic health scales, the SF-36 and Health Assessment Questionnaire (HAQ) [44]. It was originally intended for use in large randomised controlled trials for patients undergoing total knee replacement, to assess levels of, and changes in, pain and function of the knee solely from the patient's viewpoint. Data collection can be via a postal questionnaire or by directed interview.