A Safety and Effectiveness Study of Acetaminophen (4000 mg/Day) and Naproxen (750 mg/Day) in the Treatment of Osteoarthritis of the Hip or Knee

Inclusion Criteria: Osteoarthritis of the hip or knee for a minimum of six months duration requiring treatment with either an analgesic or anti-inflammatory agent on a regular basis (greater than or equal to three days/week) for at least three months History of osteoarthritis of the hip or knee characterized by pain of mild or moderate intensity Radiographic evidence of grade 2 or 3 osteoarthritis based on the Kellgren and Lawrence radiographic entry criteria Physical ability must be either American College of Rheumatology (ACR) Functional Class I or II Following the washout period, reports mild to moderately severe pain over the previous 24 hours and demonstrates a minimum increase of 20% in the WOMAC Osteoarthritis Index pain subscale score, relative to the screening score. Exclusion Criteria: History of surgery, including arthroscopy, or major trauma to the study joint in the previous 12 months Radiographic evidence of severe osteoarthritis of the study joint based on the Kellgren and Lawrence radiographic criteria of grade 4 osteoarthritis Signs of active study joint inflammation including redness, warmth, and/or, if qualifying with osteoarthritis of the knee, a large, bulging effusion of the study knee joint with the loss of normal contour of the joint at the screening visit or at the baseline examination after the washout period Morning stiffness of >30 minutes duration Significantly incapacitated or disabled and would be categorized as ACR Functional Class III (able to perform only few or none of the duties of usual occupation or self-care) or IV (largely or wholly incapacitated), or unable to walk without assistive devices