This trial was designed for comparison and evaluation of the efficacy and safety of buprenorphine transdermal patch (Norspan® patch 5 mg, 10 mg and 20mg) against oral tramadol (Tridol® SR (slow release) tablet 100mg) in patients with moderate to severe pain due to osteoarthritis.

The primary objective of this non-inferiority study with active, parallel control group is to compare and assess efficacy and safety of buprenorphine transdermal patch (Norspan® Patch 5 mg, 10 mg and 20 mg) and tramadol (Tridol® SR (slow release) Tablet 100mg) in patients with moderate to severe pain due to osteoarthritis. During the period of treatment for 8weeks, titration and maintenance is kept up after 1:1 ratio randomization.

Inclusion Criteria:

• Males and females aged more than 18 years.
• Clinical diagnosis of osteoarthritis (OA) of the hip and/or knee including fulfilling the American College of Rheumatology Criteria (ACR criteria L13) and documentation of osteoarthritis in the relevant joint.
• Patients with moderate to severe osteoarthritis pain in the relevant joint, confirmed by BS-11 (Box Scale-11) more than 4 for their pain on average during the last week, in their primary OA joint, at both the screening and base line visits despite treatment with non-opioid analgesics.

Exclusion Criteria:

• Patients being treated with high potency opioid analgesics (e.g., morphine, fentanyl, oxycodone, methadone, hydromorphone, ketobemidone, buprenorphine (including Norspan®)) for their osteoarthritis pain.
• Patients who have been taking any opioid analgesics within the last 4 weeks prior to the screening visit.
• Patients who have been using any (Non-steroidal Anti-Infammatory) NSAID transdermal preparation less than 2 weeks prior to the screening visit.