Bones of the Leg - Lecture notes 13 PDF

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Bones of the Leg...

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Bones of the Leg The tibia (TIB-e . -uh) and fibula (FIB-u . -luh) together support the leg. The slender fibula parallels the lateral border of the tibia, with the tibia medial to the fibula in anatomical position. The medial border of the thin fibula is bound to the tibia by the interosseous membrane. This membrane helps stabilize the positions of the two bones. It also provides additional surface area for muscle attachment. A cross section of the tibia and fibula is shown in Figure 8–12. The Tibia The tibia, or shinbone, is the large medial bone of the leg; its main parts (from proximal to distal) are the condyles, the shaft, and a process called the medial malleolus (Figure 8–12a). The medial and lateral condyles of the femur articulate with the medial and lateral tibial condyles at the proximal end of the tibia. The intercondylar eminence is a ridge that separates the condyles (Figure 8–12b). The anterior surface of the tibia near the condyles has a prominent, rough tibial tuberosity (see Figure 8–12a), which you can feel through the skin. This tuberosity marks the attachment of the patellar ligament. The anterior margin is a ridge that begins at the tibial tuberosity and extends distally along the anterior tibial surface. You can also easily feel the anterior margin of the tibia through the skin. As it nears the ankle joint, the tibia broadens, and the medial border ends in the medial malleolus a large process familiar to you as the medial bump at the ankle. The inferior surface of the tibia articulates with the proximal bone of the ankle. The medial malleolus supports this joint medially. The Fibula From proximal to distal, the fibula is made up of a head, shaft, and lateral malleolus process (see Figure 8–12a,b). The head of the fibula articulates with the tibia. The articular facet is located on the anterior, inferior surface of the lateral tibial condyle. As its small diameter suggests, the fibula does not help transfer weight to the ankle and foot. In fact, it does not even articulate with the femur. However, the fibula is an important site for the attachment of muscles that move the foot and toes. In addition, the distal tip of the fibula extends laterally to the ankle joint. This fibular process, the lateral malleolus, gives lateral stability to the ankle. However, forceful movement of the foot outward and backward can dislocate the ankle, breaking both the lateral malleolus of the fibula and the medial malleolus of the tibia. This injury is called a Pott’s fracture. The Tarsal Bones The tarsal bones make up the ankle. The large talus transfers the weight of the body from the tibia toward the toes. The articulation between the talus and the tibia occurs across the superior and medial surfaces of the trochlea, a spool- or pulley-shaped articular process. The lateral surface of the trochlea articulates with the lateral malleolus of the fibula.

The calcaneus (kal-KA . -ne . -us), or heel bone, is the largest of the tarsal bones (Figure 8–13a,b). When you stand, most of your weight is transferred from the tibia through the talus to the calcaneus, and then to the ground. The posterior portion of the calcaneus is a rough, knob-shaped projection....