NCT01019265.

Methods	Official title: a randomised open label parallel group study comparing Norspan patch and oral tramadol. 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) pill 100 mg) in people with moderate to severe pain due to OA. During the period of treatment for 8 weeks, titration and maintenance is kept up using 1:1 ratio randomization.
Participants	Diagnosed with OA of the hip or knee (or both) including fulfilling the ACR criteria L13 and aged ≥ 18 years
Interventions	Buprenorphine 5 mg for 8 weeks Buprenorphine 10 mg for 8 weeks Buprenorphine 20 mg for 8 weeks Tramadol 100 mg for 8 weeks
Outcomes	Major outcome: PI – Box Score‐11 pain scale Minor outcomes WOMAC Degree of sleep disturbance due to pain and improvement in quality of sleep Incidence of early discontinuation due to lack of efficacy
Notes	Study start date: March 2008 Primary completion date: March 2009 Study completion date: May 2009 Contact information: not provided ClinicalTrials.gov identifier: NCT01019265