Diclofenac gel (Voltaren Gel) can be used to treat pain from osteoarthritis in the hands, wrists, elbows, knees, ankles and feet. It may be applied four times daily. The liquid formulation (Pennsaid), which can be used for osteoarthritis of the knee, is applied twice daily. The patch (Flector Patch) is placed over the painful joint. It should be changed every 12 hours. Without insurance, the patch can be expensive, at over $100 for 10patches.