The purpose of this study is to investigate whether tight control of patients with newly diagnosed psoriatic arthritis (consisting of regular 4 weekly objective assessment of disease activity and protocol-led intensive treatment) can improve outcome as opposed to standard care (usually 3 monthly reviews with no objective outcome measures and no protocol for treatment). The principle hypothesis of this study is that tight control of inflammation in psoriatic arthritis using a treatment protocol and pre-defined objective targets for treatment will lead to an improvement in patients' disease activity and a reduction in radiological joint damage.