Feasibility Studies in the In Vivo Measurement of Iron in Synovial Membrane

Rheumathoid arthritis is a widespread and currently incurable disease. Its most obvious symptom is inflammation o£ the synovial joints; it also results in a reduced life expectancy. Certain principles of structure are common to all synovial joints (Fig. 1). They are formed by two bones in apposition, the ends being capped with a smooth surface of hyaline cartilage. The bones are held together by a sleeve, formed from an outer fibrous membrane and an inner synovial membrane; the space created between the bones is filled with synovial fluid, which acts as a lubricant. It is known that subjects with rheumatoid arthritis have increased levels of iron in the synovial membrane (Muirden, 1966) and mean levels rise from 15 g/g to 350 g/g dry tissue weight (Senator and Muirden, 1968). In addition the mass of the synovium Increases dramatically, the membrane thickening from a few cells up to 1–10 mm.