The purpose of this study is to assess the degree of pain control achieved by treatment with fentanyl, administered via adhesive patches applied to the skin ('transdermal system") in patients with rheumatoid arthritis or osteoarthritis of the knee or hip. Treatment will be administered fo r4 weeks, added on to existing therapy with other medications.

Chronic, non-cancer pain may result from injury or illness, such as rheumatoid arthritis or osteoarthritis, which causes suffering and a reduction in the quality of life. Opioids, such as fentanyl, are beneficial as potent pain-relieving drugs in patients with continuous pain. This is an open-label, prospective study to assess the degree of pain control provided by treatment with fentanyl administered through the skin via adhesive patches ("transdermal system") for 28 days in patients with rheumatoid arthritis or osteoarthritis of the hip or knee, whose pain is inadequately controlled by other medications. During the first week of treatment, a prophylactic anti-nausea and vomiting agent will be given to patients to control these symptoms that can occur during opioid therapy. After 28 days, patients who do not respond adequately to treatment will be tapered off by gradually reducing the dose of fentanyl. Assessment of effectiveness will include a rating of pain control (excellent, good, moderate, poor, very poor), Pain Assessment Questionnaire, Quality of Life Questionnaire (SF-36), Health Assessment Questionnaire (HAQ), recording of the usage of any additional pain-relieving medications, and an evaluation of the anti-nausea and vomiting treatment. Safety evaluations include incidence of adverse events, and physical examinations. The study hypothesis is that patients with rheumatoid arthritis or osteoarthritis of the hip or knee whose pain is not adequately controlled by other medications will show an improvement in pain control after 28 days of treatment with the fentanyl transdermal system. Fentanyl transdermal patches to deliver from 25 micrograms/hr to 100 micrograms/hr, changed every 3 days, for 28 days; doses may be adjusted for adequate pain control, Anti-nausea tablets (Metoclopramide, 10 mg, 3 times/day) during first week. Paracetamol tablets (500mg) to supplement pain control.

Inclusion Criteria:

• Patients must meet the American College of Rheumatology criteria for rheumatoid arthritis (RA) or osteoarthritis (OA) of the hip or knee and have moderate or severe pain that is not adequately controlled by other medications (paracetamol (acetaminophen), NSAIDs, COX-2 inhibitors, weak opioids)
• OA patients must be in need of and waiting for hip or knee replacement
• RA patients using disease modifying antirheumatic drugs (DMARDs) must have been on stable dose of medication for >=3 months.

Exclusion Criteria:

• Patients who have received regular treatment with strong opioids during the month prior to study
• another continuous pain that stands out compared to RA or OA pain
• skin disease or known allergy or hypersensitivity to fentanyl or to the adhesives
• history of liver disease
• new physical therapy or change in that therapy within one month of study
• pregnant or nursing females, or those without adequate contraception.