A Study Comparing the Effectiveness and Safety of Extended Release Tramadol HCl at 100 mg, 200 mg and 300 mg Doses to Placebo for the Treatment of Moderate to Severe Pain Due to Osteoarthritis (OA)

Inclusion Criteria: * Patients with American College of Rheumatology (ACR) Functional Class I-III OA of the knee or hip; * Patients with involvement of knee or hip joint that warrants treatment with COX-2 selective inhibitors, NSAIDs, acetaminophen, or opioid analgesics for at least 75 of the 90 days preceding the screening visit; * Patients with a pain intensity score in index joint \>= 40 mm on the visual analog scale(VAS) at the baseline visit; * Patients who are able to discontinue acetaminophen, NSAIDS, COX-2 selective inhibitors and other analgesics during the washout period and all analgesics other than the study medication throughout the study; * Patients who are able to understand the study procedures and complete the pain scales. Exclusion Criteria: * Patients with a medical condition, other than OA, uncontrolled with treatment or any clinically significant condition that, in the investigator's opinion, precludes study participation or interferes with the assessment of chronic pain and other OA symptoms; * Patients with a diagnoses of inflammatory arthritis, gout, pseudo-gout or Paget's disease, that, in the investigator's opinion, interferes with the assessment of pain and other symptoms of OA; * Patients with a diagnosis of chronic pain syndrome; * Patients with an ACR or a clinical diagnosis of fibromyalgia; * Patients with any other clinically significant form of joint disease or prior joint replacement surgery at the index joint; * Patients with an anticipated need for surgery or other invasive procedure in the index joint.