There are many conditions such as rheumatoid arthritis, Sjogren’s syndrome, and fibromyalgia that may have an association with symptoms of RLS. This relationship is unclear. In one study, 25 percent of individuals with rheumatoid arthritis had RLS symptoms compared to only 4 percent of those with osteoarthritis. In another study, 42 of 135 patients with fibromyalgia had RLS. The exact reason for this association is not fully understood.