To compare the analgesic efficacy and safety of ABT-652 administered twice daily (BID) to placebo in subjects with osteoarthritis (OA) of the knee.

Inclusion Criteria

• History of OA of the knee joint and meeting American College of Rheumatology (ACR) Clinical and Radiographic criteria,
• Pain score as required by the protocol at Screening and Baseline
• Willing to washout of analgesics and to follow treatment plan, visit schedules and study procedures.

Exclusion Criteria

• History of sensitivity to histamine medications, acetaminophen (paracetamol), or non-steroidal anti-inflammatory drugs (NSAIDs)
• Active gastrointestinal (GI) disease, GI bleeding or GI ulceration, or history of GI bleeding or GI ulceration in the last 6 months
• History of major psychiatric disorders
• Diagnosis of rheumatoid arthritis, autoimmune disorder, arthritis other than osteoarthritis involving the study joint, or other painful syndrome that could interfere with the assessment of pain at the study joint
• Any cardiac, respiratory, neurological or other medical condition or illness that is not well controlled with treatment