that fits into the acetabulum. Two processes called the greater and lesser trochanters are at the proximal end for the attachment of muscles. The neck of the femur, located between the head and the trochanters, is the site on the femur most frequently fractured. At the distal end are two bony prominences, called the lateral and medial condyles, which articulate with the tibia and the patella. Patella.—The patella is a small oval-shaped bone overlying the knee joint. It is enclosed within the tendon of the quadriceps muscle of the thigh. Bones like the patella that develop within a tendon are known as sesamoid bones. Tibia.—The tibia, or shin bone, is the larger of the two leg bones and lies at the medial side. The proximal end articulates with the femur and the fibula. Its distal end articulates with the talus (one of the foot bones) and the fibula (fig. 1-25). A prominence easily felt on the inner aspect of the ankle is called the medial malleolus. Fibula.—The fibula, the smaller of the two leg bones, is located on the lateral side of the leg, parallel to the tibia. The prominence at the distal end forms the outer ankle and is known as the lateral malleolus. Tarsus.—The tarsus, or ankle, is formed by seven tarsal bones: medial cuneiform, intermediate cuneiform, lateral cuneiform, cuboid, navicular, talus, and calcaneus. The strongest of these is the heel bone, or calcaneus. Metatarsus.—The sole and instep of the foot is called the metatarsus and is made up of five metatarsal bones (fig. 1-25). They are similar in arrangement to the metacarpals of the hand. Phalanges.—The phalanges are the bones of the toes and are similar in number, structure, and arrangement to the bones of the fingers. JOINTS LEARNING OBJECTIVE: Recognize joint classifications and identify joint movements for the key joints in the body. Wherever two or more bones meet, a joint is formed. A joint binds various parts of the skeletal system together and enables body parts to move in response to skeletal muscle contractions. JOINT CLASSIFICATIONS Joints are classified according to the amount of movement they permit (fig. 1-26). Joint classifications are as follows:  Immovable. Bones of the skull are an example of an immovable joint. Immovable joints are characterized by the bones being in close contact with each other and little or no movement occurring between the bones.  Slightly movable. In slightly movable joints, the bones are held together by broad flattened disks of cartilage and ligaments (e.g., vertebrae and symphysis pubis). 1-15 HM3f0125 METATARSUS TARSUS PHALANGES METATARSALS MEDIAL CUNEIFORM NAVICULAR TALUS TIBIA FIBULA CALCANEUS TALUS NAVICULAR CUBOID LATERAL CUNEIFORM INTERMEDIATE CUNEIFORM MEDIAL CUNEIFORM PROXIMAL PHALANX MIDDLE PHALANX DISTAL PHALANX TARSALS METATARSALS PHALANGES Figure 1-25.—The foot: A. Lateral view of foot; B. Right foot viewed from above.