[The enthesis. Physiological morphology, molecular composition and pathoanatomical alterations].

The composition of the extracellular matrix in tendons and ligaments is directly related to the mechanical environment. Local compression triggers functional adaptation that leads to cartilage-specific transformation of the tissue. The molecular composition of the extracellular matrix at the enthesis is related to the amount of stress and to the geometry of the insertion. Comparison of physiologically and non-physiologically loaded entheses shows that only certain molecules occur under relatively high amounts of local compressive stress. The occurrence of certain cartilage specific molecules is clinically relevant, because some of these molecules have been identified as autoantigens during the autoimmune response in patients with rheumatoid arthritis. These molecules constitute potential targets for the manifestation of rheumatoid arthritis at fibrocartilaginous entheses.