Copyright Goodheart-Willcox Co., Inc. Chapter 5 The Skeletal System 151 with walking and running by acting like a spring that stores and releases energy. As Figure 5.32 shows, the hindfoot is constructed of tarsal bones. The two largest, the talus (TAY-lus) and calcaneus (kal-KAY-nee-us), or heel bone, bear most of the weight of the body. The five metatarsal bones that support the midfoot region are similar to the metacarpals of the hand. Like the fingers, each toe has three phalanges, and like the thumb, the big toe has only two phalanges. The toes increase the area of the foot during weight-bearing activities, such as walking and running, thereby increasing body stability. articulation with the femur at the knee joint, but the distal (lower) end of the fibula has a bony prominence called the lateral malleolus. You can readily touch and feel this prominence on the lateral (outer) side of the ankle. Like the radius and ulna in the forearm, the tibia and fibula are connected along their lengths by an interosseous membrane, and they articulate at both ends of the fibula (Figure 5.31). Ankle and Foot The ankle and foot serve the critically important functions of supporting body weight and enabling locomotion. The foot is so well designed that it assists Articulating Bones of the Leg and Ankle Joint Notched Bone or Socket Joining Bone or Region iliofemoral (hip) joint acetabulum femur tibiofemoral (knee) joint tibia femur patellofemoral joint patella anterior knee tibiofibular joints (proximal and distal) tibia fibula Figure 5.31 Goodheart-Willcox Publisher A Superior view B Inferior view Distal phalanx 1 Proximal phalanx 1 Metatarsal Medial cuneiform Intermediate cuneiform Lateral cuneiform Navicular Talus Trochlear surface of talus Distal phalanx 5 Middle phalanx 5 Proximal phalanx 5 Cuboid Calcaneus Tuberosity of calcaneus Phalanges Metatarsal bones Tarsal bones 1 2 3 4 5 1 2 3 4 5 Head Body Base © Body Scientific International Figure 5.32 Superior (A) and inferior (B) views of the bones of the right foot.