NCT00426647.

Methods	Official title: a randomised double‐blind multicentre equivalence study with active parallel comparator group to evaluate the efficacy and safety of Norspan® patches versus tramadol in subjects with chronic, moderate to severe osteoarthritis pain in the hip, knee &/or lumbar spine. Randomized, double‐blind, multicenter equivalence study with active comparator, parallel group, to evaluate the efficacy and safety of Norspan® patches vs tramadol in people with OA pain in hip, knee, lumbar spine, or a combination of these, currently receiving suboptimal analgesic treatment (defined as BS‐11 score > 4) when treated with acetaminophen 4000 mg/day or another analgesic at least comparable to this. 4 phases: run‐in, washout, double‐blind and follow‐up
Participants	Diagnosed with OA pain in hip, knee, lumbar spine, or a combination of these and aged ≥ 18 years.
Interventions	Tramadol Buprenorphine
Outcomes	Major outcome: efficacy of Norspan® Minor outcome: safety and general satisfaction
Notes	Study start date: February 2007 Primary completion date: July 2009 Study completion date: August 2009 Contact information: Address: GP, Noerretorv 10, DK‐7200 Grindsted, Denmark, Olavi, Airaksinen DM (principal investigator), Oma Lääkäri Oy, Vuorikatu 20, FIN‐70100 KUOPIO Email: olavi.airaksinen@kuh.fi Email: norpharma@norpharma.dk ClinicalTrials.gov identifier: NCT00426647