Voltaren Gel (diclofenac sodium topical gel) is a non-steroidal anti-inflammatory (NSAID) medication for use in treating pain associated with osteoarthritis in joints amenable to topical treatment such as the knees and hands. Described as "an important clinical milestone", the US approval means patients have a further option to treat osteoarthritis pain, which affects approximately 21 million people in the US. Clinical trials have demonstrated Voltaren Gel to be highly effective in treating osteoarthritis pain in the hands and knees, which are the bodies most affected joints. It is the first topical treatment to prove this, with its systemic absorption 94 per cent less than the comparable oral diclofenac treatment, thereby minimising the risk of side effects. The US Food and Drug Administration approval was based on several studies. In one, 46 per cent of patients with osteoarthritis of the hand experienced reduced pain levels after six weeks. In another, 51 per cent of patients with osteoarthritis of the knee felt a reduction in pain after 12 weeks. "The combination of benefit and safety provides a welcome new treatment approach for osteoarthritis, offering patients an alternative to oral therapies," said Roy Altman, Professor of Medicine in the division of rheumatology and immunology at UCLA in Los Angeles and past president of the Osteoarthritis Research Society International. Osteoarthritis is a chronic condition characterised by the breakdown of cartilage in the joint.