Avulsion fracture of the calcaneal tuberosity is an uncommon injury. Usually it occurs from indirect trauma, and can be seen in old patients with osteoporosis or in patients with diabetic neuropathy. Follow-up studies showed healing of the fracture in most cases, but skeletal deformity may develop in some cases. Therefore we should take plain X-ray evaluations in diabetic patients with foot and ankle pain, even though there have been no definite trauma history. Four cases of calcaneus avulsion fracture were treated operatively in diabetic patients, and reported.