Seronegative Oligoarthritis of the Knee Study (SOKS)

Inclusion Criteria: * Inflammatory oligoarthritis (4 or less active joints) with at least one swollen knee joint of at least 3 months duration * Rheumatoid factor and anti-CCP Ab negative * Either arthritis onset at \<45 years of age, or arthritis onset at ≥45 years of age with early morning stiffness\>30mins or raised inflammatory markers * If under 40 years of age, clinical exclusion of a diagnosis of gout. * If 40 years or older at screening, a prior normal examination of synovial fluid from the affected joint excluding crystal arthropathy or infection. * Failure of methotrexate (inefficacy after \>3 month trial, intolerance or contra-indication) * Have the capacity to understand and sign an informed consent form. * Gender: male or female * 18 years of age or over. * Women must be either postmenopausal (no menstrual period for a minimum of 1 year) or surgically sterilized or in use of adequate birth control measures and have a negative serum pregnancy test on entry in the study. * Men and women of childbearing potential must use adequate birth control measures (e.g., abstinence, oral contraceptives, intrauterine device, barrier method with spermicide, implantable or injectable contraceptives or surgical sterilization) for the duration of the study and should continue such precautions for 6 months after receiving the last infusion. * Are considered eligible according to the tuberculosis (TB) eligibility assessment, screening, and early detection of reactivation rules defin…