Fractures of the tibial plateau are seen frequently in orthopedic trauma units and traditionally classified based on two-dimension plain radiographs with the Schatzker Classification system, the most popular. This system focuses on fractures involving the medial and lateral plateau but does not comment on fractures that involve the posterior aspect of the tibial plateau. The purpose of this study was to investigate the incidence of posterior tibial plateau fracture and propose a new computed tomography (CT)-based three-column classification system to guide fracture treatment. Between January 2008 and December 2009, 525 tibial plateau fractures admitted to a level 1 trauma center were retrospectively analyzed by four orthopedic trauma surgeons. Antero-posterior plain radiographs were used for Schatzker classification. CT imaging was used to further classify the fracture types with axial views dividing the plateau into three columns: a lateral, medial, and posterior. Posterior tibial plateau fracture (PTPF) was defined as a fracture with an independent fragment of the posterior column PTPFs were found in 151 cases and had an incidence of 28.8 % in this studied population. Except for type III, PTPFs were observed in each type of the Schatzker classification system. The Schatzker type VI, V, and IV fractures had the three highest percentages of PTPFs, with 76.1, 51.2, and 22.4 %, respectively. Fractures of the posterior tibial plateau are not uncommon, especially in high-energy trauma. CT imaging is required to appreciate these fracture patterns, and a three-column classification allows for a better understanding of the fracture morphology and the injury mechanism, which guides surgical management.