To compare the efficacy and safety of celecoxib versus placebo for the treatment of knee osteoarthritis (OA) in patients who were unresponsive to prescription strength naproxen and ibuprofen or who could not tolerate prescription strength naproxen and ibuprofen

Inclusion Criteria:

Inclusion criteria:

• Diagnosed, active, and symptomatic OA of the knee in a flare state with a functional capacity class of I-III at baseline visit
• Failed adequate trials of both naproxen and ibuprofen (prescription strength) within the past 5 years due to lack of efficacy, tolerability, or both; duration of prescription strength ibuprofen and naproxen must have been a minimum of 2 weeks for each drug at the respective recommended doses if failure was due to lack of efficacy, and for any duration if failure was due to lack of tolerability

Exclusion Criteria:

Exclusion criteria:

• Inflammatory arthritis or gout/pseudo-gout with acute flare within the past 2 years (subjects with fibrositis or fibromyalgia will not be excluded)
• Received acetaminophen within 24 hours of the baseline visit
• Use of a mobility assisting device for less than six weeks prior to study screening or use of a walker
• History of gastrointestinal (GI) perforation, obstruction, or bleeding
• Diagnosed or treated for GI ulcer within 60 days prior to first dose of study medication
• Received corticosteroids or hyaluronic acid within certain timeframe before study