It is responsible for transmitting the majority of the body's weight from the talus bone to the ground. Calcaneal fractures are categorized as intra-articular or extra-articular on the basis of subtalar joint involvement. Intra-articular fractures are more common and involve the posterior talar articular facet of the calcaneus. The Sanders classification groups these fractures into four types based on the location of the fracture at the posterior articular surface. Extra-articular fractures are less common and may be located anywhere outside the subtalar joint. Extra-articular fractures are categorized depending on whether the involvement of the calcaneus is anterior (Type A), middle (Type B) or posterior (Type C). The Angle of Gissane, or "Critical Angle", is the angle formed by the downward and upward slopes of the calcaneal superior surface. On a lateral radiograph, an angle of Gissane > 130° suggests fracture of the posterior subtalar joint surface. Böhler's angle, or the "Tuber Angle", is another normal anatomic landmark seen in lateral radiographs. It is formed by the intersection of 1) a line from the highest point of the posterior articular facet to the highest point of the posterior tuberosity, and 2) a line from the former to the highest point on the anterior articular facet. Böhler's angle is normally 25° to 40°. It is named after Austrian physician Lorenz Böhler. A decreased angle is indicative of a calcaneal fracture. The Sanders classification system is the most commonly used system for categorizing intra-articular fractures. There are 4 types: Type I fractures are non-displaced fractures (displacement < 2 mm). Type II fractures consist of a single intra-articular fracture that divides the calcaneus into 2 pieces. Type IIA: fracture occurs on lateral aspect of calcaneus. Type IIB: fracture occurs on central aspect of calcaneus. Type IIC: fracture occurs on medial aspect of calcaneus. Type III fractures consist of two intra-articular fractures that divide the calcaneus into 3 articular pieces. Type IIIAB: two fracture lines are present, one lateral and one central. Type IIIAC: two fracture lines are present, one lateral and one medial. Type IIIBC: two fracture lines are present, one central and one medial. Type IV fractures consist of fractures with more than three intra-articular fractures. Extra-articular fractures include all fractures that do not involve the posterior facet of the subtalar joint. Type A involve the anterior calcaneus Type B involve the middle calcaneus. This includes the sustentaculum tali, trochlear process and lateral