An Evaluation of the Optimal Dose of Tofacitinib Needed to Achieve Low Disease Activity (LDA) or Clinical Remission in Patients With Active Rheumatoid Arthritis (RA) as Measured From a Clinical and Structural Perspective

Inclusion Criteria: 1. Patient must be at least 18 years old at the screening visit 2. Patient must be able to understand the information provided to them and give written Informed Consent 3. Female subjects of childbearing potential must test negative for pregnancy 4. Male and female subjects of childbearing potential must agree to use two highly effective methods of contraception throughout the study and for at least 3 months after the last dose of tofacitinib. 5. Female patients who are not of childbearing potential must either be postmenopausal for at least 12 months or have undergone a documented hysterectomy and/or bilateral oophorectomy. 6. Patients can be naïve to biologic therapy or have had exposure to TNF or biologic therapy (see appropriate wash out schedule) and be experiencing at least a moderate disease activity score as determined by a CDAI of \> 10 at Screening despite currently receiving Methotrexate therapy at a dose of 10-25 mg/weekly for at least 12 weeks and at a stable dose for the past 4 weeks. 7. Patients on prednisone must be receiving a daily dose of \< 10 mg. 8. Subjects must screen negative for active tuberculosis (TB) by either a PPD or a QuantiFERON Gold test (unless previously performed and documented within 3 months prior to screening). If patient tests positive for latent TB at screening, the chest X-ray at Screening must be negative for active TB and the patient must be started on ( or have completed) an adequate course of therapy for latent tuberculosis at the Baseline visit. Patient must complete the entire 9 month course of treatment for latent TB. 9. Chest radiograph taken at screening (unless taken and documented within 3 months prior to screening) must be negative for active TB and have non clinically significant medical findings. 10. Patients must be able and willing to comply with the requirements of the study protocol Exclusion Criteria: 1. Patients who have a history of any inflammatory disease which would be interfere with outcome measurement 2. Patients who in the Investigator's opinion have a medical condition in which participation in this trial is contraindicated 3. Patients who have received intramuscular, intravenous, or intraarticular (IM/IV/IA) corticosteroids 28 days prior to baseline. 4. Patients who have active TB or a history of active TB (positive PPD skin test \>5mm and a positive chest x-Ray) or patients who have come in close contact with an individual with active TB. 5. Patients with a history of acute or chronic viral hepatitis B or C or those who test positive at screening. 6. Patients with a known human immunodeficiency virus (HIV) infection. 7. Concurrent malignancy or a history of malignancy other than a non-metastatic basal cell or squamous cell cancer of the skin or cervical carcinoma in situ. 8. Patients who have a metal device affected by MRI (e.g. any type of electronic, mechanical or magnetic implant; cardiac pacemaker; aneurysm clip(s); implanted cardioverter defibrillator; or cochlear implant) 9. Patients who have potential ferromagnetic foreign body (metal slivers metal shavings, other metal objects) for which they have sought medical attention 10. Patients at a high risk of infection in the Investigator's opinion or have had recurrent infections requiring hospitalization or parenteral antimicrobial therapy within the past 6 months. 11. Patients with an adverse reaction to tofacitinib 12. Patients with any other condition (e.g., clinically significant laboratory values) which in the Investigator's judgment would make the patient unsuitable for inclusion in this study 13. Patients who have received prohibited medications: the following approved biological therapy for RA: etanercept, adalimumab, anakinra, abatacept, tocilizumab within 28 days of baseline * rituximab within 9 months of baseline * infliximab within 56 days of baseline * DMARDs other than methotrexate within 28 days of baseline * any experimental biologic agent within three months or 5 half-lives prior to baseline * exposure to JAK inhibitor 14. Female patients who are breast-feeding, pregnant, or plan to become pregnant during the trial or within twelve weeks following last dose of study drug