Inclusion Criteria:

• If female and of childbearing potential, must be using adequate contraception since last menses and will use adequate contraception during the study,
• Diagnosed as having OA of the knee
• Functional Capacity Classification of I-II (FCC)
• If on active analgesic or anti-inflammatory pain medication, must have VAS pain score>=30mm in signal knee related to walking on a flat surface within the previous 48 hours. Subjects who are not taking any pain medication must have a VAS pain score>=40mm in the signal knee
• At baseline visit, must have a history of pain in the signal knee>=40mm when walking on the flat within the previous 48 hours.
• In the Investigator's opinion, the patient requires and is eligible for therapy with an anti-inflammatory analgesic.
• If on an NSAID or analgesic, patient must have completed a washout period prior to baseline assessments that is a minium of five half lives.
• The patient has provided written informed consent before undergoing any study procedures.

Exclusion Criteria:

• Diagnosed as having inflammatory arthritis or acute trauma at the index joint.
• Another painful condition that would interfere with his/her ability to walk or to make reasonable assessments of their pain.
• Received an injection of corticosteroid into the signal knee within 3 months; or with a hyaluronan produce in the signal knee within the previous 6 months.
• Requires the use of a cane or other assistive device to complete the walk.
• Known cardiovascular disease which has been symptomatic in the past 12 months
• History of blood clots or is at any increased risk for blood clotting.
• Asthma or any breathing condition which would preclude walking briskly for 20 consecutive minutes or 40 minutes total.
• Has taken any NSAIDs, COX-2 inhibitors, or any analgesic, with the exception of the rescue acetaminophen, within two days prior to Visit 2
• Active malignancies or any type or a malignancy that has recurred within 5 years before enrollment.
• Diagnosed as having or has been treated for esophageal, gastric, pyloric channel, duodenal ulceration within 90 days
• Active GI disease, a chronic or acute renal or hepatic disorder, or a significant coagulation defect.
• Any chronic illness or laboratory abnormalities considered to be clinically significant.
• Received any investigational medication within 30 days
• Known hypersensitivity to celecoxib, NSAIDs, to sulfonamides

• Use of the following drugs:

  1. NSAIDs or COX-2 specific inhibitors
  2. Analgesics except rescue medication within 24 hours of a study visit
  3. Anticoagulants
  4. Lithium
  5. Glucosamine or chondroitin sulfate are excluded unless on stable dose for at least 3 months