I assume you are talking about Rheumatoid Arthritis. If so, the major difference is in the cause of the disease, not in the effects.
RA is an autoimmune disease. It is caused by the body's immune system attacking the body's own tissues by mistake. By contrast, osteoarthritis is a "wear and tear" issue. It is caused simply by the use of joints whose cartilage gets worn away by that use over time.