A recurrent aneurysmal bone cyst of the proximal phalanx of the index finger of a three-year-old child, treated with bioactive glass, is presented. Over a two-year follow-up, the treated area appeared dense on X-rays. At two years, no cavity was observed and the homogenous region resembled normal trabecular bone. The phalanx had grown in length and remodelled to an almost normal shape.