How Does Rheumatoid Arthritis Usually Start?. Rheumatoid arthritis is the most common form of inflammatory arthritis worldwide, affecting approximately 1 in 100 people at some point during their lifetime. Up to 35 percent of working-age people who develop RA are disabled within 10 years of their diagnosis. Newer treatments can slow the progression of RA, but early diagnosis is essential for preventing the irreversible joint damage associated with this disease. Because the early symptoms of RA are sometimes deceptive and nonspecific, diagnosis may be delayed.