After blunt trauma to the distal phalanx of any digit, a patient can develop a subungual hematoma. The hematoma is contained between the nail plate and the sterile matrix of the nail bed, which is highly vascularized. Unless artificial nails are present, the collecting blood is easily visualized as a dark blue-black discoloration under the nail (Fig. 156.1). The bleeding into the potential space underneath the nail plate compresses the sterile matrix, which can cause significant discomfort.