HKT-500 in Adult Patients With Osteoarthritis (OA) Knee Pain

Inclusion Criteria: * man or woman ≥45 years of age. * clinical diagnosis of unilateral or bilateral OA of the knee * taking an NSAID or acetaminophen on a regular basis and has a history of knee pain amelioration with NSAID or acetaminophen use. * mild to moderate OA of the knee at the screening visit * subject exhibits an arthritis "flare" in the target knee within 7 days day of withdrawing from a NSAID or acetaminophen. * subject understands that treatment will be administered on an inpatient basis. * subject is capable of understanding and complying with the protocol and has signed the informed consent document. Exclusion Criteria: * subject is a woman of childbearing potential who has a positive urine pregnancy test, is lactating, or who is not surgically sterile * subject has symptoms that are attributable to primary inflammatory diseases of the joint * subject has unstable knees including a history of the knee catching or giving way or physical examination evidence of instability * subject has arthropathies that occur in conjunction with systemic diseases * subject has a chronic pain condition * subject is grossly obese * subject has a history of knee surgery within the past 12 months or arthroscopy within the past 6 months. * subject has a history of osteotomies. * subject is not willing to discontinue the use of NSAIDs, acetaminophen or other prohibited treatments * subject used opioids for OA pain within 1 month