NCT00832416.

Methods	Study title: a four‐arm study comparing the analgesic efficacy and safety of tramadol once a day 100, 200 and 300 mg versus placebo for the treatment of pain due to osteoarthritis of the knee. Methods not provided.
Participants	Diagnosed with moderate to severe OA of the knee, consistent with the ACR clinical classification criteria for arthritis of the knee, and aged 40–75 years
Interventions	Tramadol 100 mg daily Tramadol 200 mg daily Tramadol 300 mg daily Placebo
Outcomes	Major outcomes Patient global rating of pain for the study period (12 weeks) Percentage difference between WOMAC Pain subscale score from baseline to end of study (week 12) Percentage difference between WOMAC Physical Function subscale score from baseline to end of study (week 12) Minor outcomes Percentage difference in WOMAC Pain subscale score from baseline to intervening visits (visits 2–4) Percentage difference in WOMAC Physical Function subscale score from baseline to intervening visits (visits 2–4) Multiple dose effect using 24‐hour VAS Pain Questionnaire Investigator global rating of pain relief Percentage of participants who dropped out from trial by dropout reason
Notes	Study start date: January 2003 Primary completion date: August 2003 Contact information: Address: 480 boulevard, Armand‐Frappier, Laval, Québec, H7V 4B4 Email: info@labopharm.com Phone: 450 680‐2444 ClinicalTrials.gov identifier: NCT00832416