Pennsaid (diclofenac sodium) is an expensive non-steroidal anti-inflammatory drug (NSAID). It is used to treat osteoarthritis of the knees. It is slightly more popular than comparable drugs. It is available in generic and brand versions. The most common version of Pennsaid is covered by 53% of insurance plans at a co-pay of $60.00-$87.50, however, some pharmacy coupons or cash prices may be lower. With the Patient Assistance Program from HealthWell Foundation, contact the program to see how they can financially help you out.