The coxal (hip) joint is the point where the head of the femur inserts into the acetabulum of the os coxae (fig. 9.21). Because the coxal joints bear much of the body's weight, they have deep sockets and are much more stable than the shoulder joint. The depth of the socket is somewhat greater than you see on dried bones because of a horseshoe-shaped
Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill
Physiology: The Unity of Companies, 2003 Form and Function, Third Edition
Chapter 9 Joints 313
Anterior
Anterior
Humerus
Medial epicondyle
Ulnar collateral ligament
Ulna
Medial
Lateral epicondyle
Joint capsule Radial collateral ligament
Annular ligament
Tendon of biceps brachii (cut)
Radius
Trochlea Joint capsule Coronoid process Radius
Medial
Humerus
Medial epicondyle
Ulnar collateral ligament
Ulna
Trochlea Joint capsule Coronoid process Radius
Medial
Humerus
Olecranon bursa
Articular cartilage Olecranon
Humerus
Ulna
Medial
Annular ligament
Tendon of biceps brachii (cut)
Ulna
Humerus
Joint capsule
Tendon of triceps brachii
Ulnar collateral ligament
Olecranon bursa
Coronoid process
Annular ligament
Tendon of biceps brachii (cut)
Radius
Humerus
Lateral epicondyle
Radial collateral ligament
Joint capsule
Olecranon (d)
Lateral
Lateral
Humerus
Joint capsule Annular ligament
Tendon of biceps brachii (cut)
Radius
Ulna
Humerus
Joint capsule
Tendon of triceps brachii
Ulnar collateral ligament
Olecranon bursa
Coronoid process
Joint capsule Annular ligament
Tendon of biceps brachii (cut)
Radius
Ulna
Olecranon bursa
Articular cartilage Olecranon
Figure 9.20 The Elbow Joint. (a) Anterior view; (b) midsagittal section, medial view; (c) medial view; (d) lateral view.
ring of fibrocartilage, the acetabular labrum, attached to its rim. Dislocations of the hip are rare, but some infants suffer congenital dislocations because the acetabulum is not deep enough to hold the head of the femur in place. This condition can be treated by placing the infant in traction until the acetabulum develops enough strength to support the body's weight (fig. 9.22).
Ligaments that support the coxal joint include the iliofemoral (ILL-ee-oh-FEM-oh-rul) and pubofemoral (PYU-bo-FEM-or-ul) ligaments on the anterior side and the ischiofemoral (ISS-kee-oh-FEM-or-ul) ligament on the posterior side. The name of each ligament refers to the bones to which it attaches—the femur and the ilium, pubis, or ischium. When you stand up, these ligaments become twisted and pull the head of the femur tightly into the acetabulum. The head of the femur has a conspicuous pit called the fovea capitis. The round ligament, or liga-mentum teres24 (TERR-eez), arises here and attaches to the lower margin of the acetabulum. This is a relatively slack ligament, so it is questionable whether it plays a significant role in holding the femur in its socket. It does, however, contain an artery that supplies blood to the head of the femur. A transverse acetabular ligament bridges a gap in the inferior margin of the acetabular labrum.
24teres = round
Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition
314 Part Two Support and Movement
Ilium
Iliofemoral ligament
Greater trochanter
Femur
Pubofemoral ligament
Pubis-
Anterior
Iliofemoral ligament
Greater trochanter
Femur
Lesser trochanter
Pubofemoral ligament
Pubis-
Anterior
Iliofemoral ligament
Iliofemoral ligament
Greater trochanter
Ischial tuberosity
Posterior
Greater trochanter
Ischial tuberosity
Posterior
Femur
Acetabulum
Labrum
Acetabulum
Labrum ligament (cut)
Ligamentum teres (cut)
Fovea capitis
Head of femur Greater trochanter
Femur
ligament (cut)
Ligamentum teres (cut)
Fovea capitis
Head of femur Greater trochanter
Femur
Transverse acetabular ligament
Acetabular labrum Acetabulum
Round ligament Head of femur
Greater trochanter
Shaft of femur
Transverse acetabular ligament
Greater trochanter
Figure 9.21 The Coxal (hip) Joint. (a) Anterior view; (b) posterior view; (c) the acetabulum with the femoral head retracted; (d) photograph of the right hip with the femoral head retracted, anterior view.
Figure 9.22 Treatment of Congenital Hip Dislocation. Infants are sometimes placed in traction to treat this condition.
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