In many cases, the presence of psoriasis is the determining and distinguishing factor that helps a physician to make the diagnosis of psoriatic arthritis. November 8, By Joan Bathon, M. The three most common types of arthritis, osteoarthritis, rheumatoid arthritis, and psoriatic arthritis, have many overlapping symptoms, sometimes making the diagnosis of psoriatic arthritis difficult. So what is psoriatic arthritis ( PsA) and how does it differ from rheumatoid arthritis ( RA)? Well, just like rheumatoid arthritis, it is an auto- immune disease. Psoriatic arthritis ( PsA) and osteoarthritis ( OA) are two of the most common forms of arthritis. Rheumatoid osteoarthritis psoriatic arthritis. Jan 09, · Arthritis and Rheumatic Diseases Ankylosing Spondylitis Autoimmune Diseases Autoinflammatory Diseases Arthritis Arthritis and Rheumatic Diseases Behçet’ s Disease Giant Cell Arteritis Gout Heritable Disorders of Connective Tissue Juvenile Arthritis Lupus Polymyalgia Rheumatica Reactive Arthritis Psoriatic Arthritis Rheumatoid Arthritis. What is the difference between Osteoarthritis and Psoriatic Arthritis? Psoriatic arthritis and osteoarthritis Question. It causes joint swelling, stiffness, and pain. Both cause an erosive inflammatory arthritis ( pain, stiffness and swelling) in addition to chronic fatigue. How can the answer be improved? How Is Psoriatic Arthritis Diagnosed? PsA is an autoimmune disease.