Rheumatology (Greek ῥεῦμα, rheûma, flowing current) is a branch of medicine devoted to the diagnosis and management of disorders whose common feature is inflammation in the bones, muscles, joints, and internal organs. Rheumatology covers more than 100 different complex diseases, collectively known as rheumatic diseases, which includes many forms of arthritis as well as lupus and Sjögren's syndrome. Doctors who have undergone formal training in rheumatology are called rheumatologists.
Many of these diseases are now known to be disorders of the immune system, and rheumatology has significant overlap with immunology, the branch of medicine that studies the immune system.