Ketoprofen in a topical patch formulation has been demonstrated to be effective for treating mild to moderate pain caused by various musculoskeletal disorders.

The objective of this study is to demonstrate the short-term multiple dose efficacy and safety of HKT-500 in subjects with pain caused by mild to moderate osteoarthritis of the knee. The goal of the study is to gather additional information about the analgesic efficacy and safety of repeated, 24-hour applications of 2 HKT-500 patches per knee for a total of 28 days in subjects with pain caused by mild to moderate osteoarthritis of the knee.

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