[The tuberositas phalangis distalis of the fingers as enthesis and its normal reactions at the margins].

The ungual tuft of the digits corresponds to an enthesis at which usually numerous reactions take place especially in adults. These reactions are to be classified into formation and reduction of bone. The formation of bone is the dominant reaction and causes diagnostic problems only in irregular shapes. On the contrary, the usual reduction of bone after the preceding formation causes more diagnostic problems because the borderline to pathology is a flowing one. Reductions of bone demand a meticulous observation of possible further osseous changes to record systemic enthesopathic or high-bone turnover situations in their early or minimal stages.