enthesis

An enthesis is the connective tissue at the site where a tendon or ligament inserts into bone, and its function is to transmit tensile load from soft tissue to the skeleton. Two structural types are recognised. Fibrous entheses attach directly to bone or periosteum primarily through fibrous tissue, whereas fibrocartilaginous entheses attach through a transitional layer of fibrocartilage interposed between the fibrous tendon tissue and the bone. That graded transition distributes stress across an interface between materials of very different stiffness. Recurring stress or inflammatory autoimmune disease can cause inflammation of the enthesis and, occasionally, fibrosis and calcification. Two subordinate structures are recorded beneath this entry, corresponding to the two types.