• Average pain intensity over the preceding 24 hours evaluated at the last timepoint or 29 days using a visual scale.
  

• Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index at the last timepoint or 29 days
  

Arthritis is the most common chronic debilitating disease in the United States (more than 43 million people or 1 in 6). Osteoarthritis of the knee is a very common and a major cause of disability. Pharmacological treatment includes the following analgesics: non-steroidal anti-inflammatory drugs (NSAIDs), cyclo-oxygenase II (COX-II) inhibitors, acetaminophen and opioids. Despite the numerous available analgesic medications, 60% to 80% of patients suffering from chronic pain are currently treated inadequately. Opioid analgesics have been shown to be efficacious in chronic non-malignant pain and can be an important therapeutic asset. The study was a 4-week randomized multicenter double-blind, placebo- and active-controlled, parallel-group, forced-titration phase 2B study of efficacy and safety with tapentadol extended release (ER) to 233 mg BID and oxycodone PR to 20 mg BID vs placebo in subjects with moderate to severe chronic pain of knee osteoarthritis. Primary efficacy outcome was the average pain intensity 24 hours before the last evaluation time or 29 days. Safety was evaluated by reporting of adverse events, laboratory tests, vital sign measures, ECGs. This study hypothesis was that tapentadol extended release was effective in relieving chronic moderate to severe pain from knee osteoarthritis compared to treatment with placebo using 2 dosing regimens for tapentadol.

tapentadol extended release white, fim-coated tablet taken orally twice a day during a 4-week period at a dose that steadily increased up to 100 mg or 200 mg; placebo tablets; or oxycodone extended release tablet, 20 mg.

Inclusion Criteria:

• Subjects with a clinical diagnosis of osteoarthritis of the knee based symptoms and/or radiographic criteria present for at least 3 months
• Moderate to severe chronic pain due to knee osteoarithritis

Exclusion Criteria:

• Previously opioid treated subject who had a history of withdrawal after cessation of the opioid
• History of seizure disorder, psychiatric disease and history of head trauma requiring evaluation by hospital based staff, or unconsciousness of unknown origin. Subjects who, in the investigator's judgment, have well-controlled depression or anxiety disorder may participate
• Subjects with history of uncontrolled hypertension (systolic blood pressure > 160 mmHg or diastolic blood pressure > 95 mmHg)
• Intake of tricyclic antidepressants, serotonin norepinephrine reuptake inhibitors, barbiturates, neuroleptics, monoamine oxidase inhibitors, and antiparkinsonian drugs within the 30 days prior to the screening visit