This is a Randomized, Double-Blind, Placebo-Controlled, Parallel-Design, Multiple-Site Clinical Study to Evaluate the Therapeutic Equivalence of Diclofenac Sodium Gel, 1% (Glenmark Pharmaceuticals Ltd) to Voltaren® Gel (Diclofenac Sodium topical gel) 1% (Novartis Consumer Health, Inc) in Patients with Osteoarthritis (OA) of the Knee

Inclusion Criteria:

1. Healthy male or non-pregnant female aged ≥ 35 years with a clinical diagnosis of OA of the knee according to the American College of Rheumatology (ACR) criteria.
2. OA Symptoms for at least 6 months prior to screening.
3. Baseline Western Ontario McMaster Osteoarthritis (WOMAC) pain subscale of > 9 on a 20 point scale for the target knee immediately prior to randomization.

Exclusion Criteria:

1. History of OA pain in the contralateral knee requiring medication within 1 year prior to screening.
2. History of secondary OA, rheumatoid arthritis, chronic inflammatory disease (e.g., colitis) or fibromyalgia.
3. History of gastrointestinal bleeding or peptic ulcer disease.
4. Known allergy to aspirin or nonsteroidal anti-inflammatory drug (NSAID).
5. Use of anticoagulants, ACE-inhibitors, cyclosporine, diuretics, lithium, or methotrexate prior to 30 days of screening.
6. Concomitant use of systemic corticosteroids, topical corticosteroids, or immunosuppressive drugs or their use prior to 30 days of screening.