This study aims to better understand the way in which painful osteoarthritis affects different people and whether an anti-inflammatory medication such as Arcoxia (etoricoxib) can help to modify this pain. The study will use questionnaires and tests of pain sensitivity to identify arthritis sufferers with more widespread, nerve-type pain and then to investigate whether a daily dose of Arcoxia is more effective than a placebo pill in reducing these symptoms and improving functional movements. The study will also be comparing the same test results of a small group of subjects without knee pain.