Inflammatory arthritis refers to diseases of the joints where the immune system causes inflammation.
These different types of arthritis all have many features in common, and it may be impossible to diagnose exactly the type of arthritis. This is especially so at the onset of the condition because early symptoms are common to all types. Nearly 70 percent of all people over age 70 show signs of the disease on X-ray exams, but only half of these people ever have symptoms. OA is the most common type of arthritis, affecting more than 16 million Americans. Almost everyone over age 75 has at least one affected joint.