To establish the therapeutic equivalence and safety of a generic Diclofenac Sodium Topical Gel, 1% with Voltaren® Gel 1% in subjects with osteoarthritis of the knee.

Inclusion Criteria:

• Healthy, ambulatory male or non-pregnant female subjects aged ≥ 35 years with a clinical diagnosis of OA of the knee.
• Had an X-ray of the target knee, taken no more than 1 year before baseline, showing evidence of OA with Kellgren-Lawrence grade 1-3 disease.
• After discontinuing all pain medications for at least 7 days, has at least moderate pain on movement for target knee
• If female and of child-bearing potential, agree to abstain from sexual intercourse or use a reliable method of contraception during the study
• Able to tolerate rescue medication with paracetamol/acetaminophen.

Exclusion Criteria:

• Pregnant or lactating or planning to become pregnant during the study period.
• X-ray showing evidence of OA with Kellgren-Lawrence grade 4 disease.
• History of OA pain in the contralateral knee requiring medication within 1 year prior to screening.
• After discontinuing all pain medications for at least 7 days, has a baseline score of ≥20 mm on a 0-100 mm Visual Analog Scale (VAS) for the contralateral knee immediately prior to randomization.
• History of secondary OA, rheumatoid arthritis, chronic inflammatory disease or fibromyalgia.
• History of asthma, hypertension, myocardial infarction, thrombotic events, stroke, congestive heart failure, impaired renal function or liver disease.
• History of gastrointestinal bleeding or peptic ulcer disease.
• Use of warfarin or other anticoagulant therapy within 30 days of study randomization.
• Elevated transaminases at screening.
• Use of ACE inhibitors, cyclosporine, diuretics, lithium or methotrexate, within 30 days of study randomization.
• Concomitant use of corticosteroids or use within 30 days of study randomization.
• Concomitant acetylsalicylic acid therapy other than a stable low dose used for cardiac prophylaxis taken for at least 3 months prior to enrollment and maintained throughout the duration of the study.
• Known allergy to aspirin or nonsteroidal anti-inflammatory drug
• Any other acute or chronic illness that could compromise the integrity of study data or place the subject at risk by participating in the study.
• Receipt of any drug as part of a research study within 30 days prior to screening.
• Previous participation in this study.
• Any use between screening and baseline of a treatment or medication that may potentially confound study assessment that may potentially confound study assessment (e.g. use of topical analgesics or anti-inflammatory drugs).
• Recent history of major knee injury or surgery.
• Known history of positive HIV