The Coxal Joint

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

Lig Collaterale Radiale

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

Biceps Radius Bursa

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

Bursa Humeri Ulna

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

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314 Part Two Support and Movement

Ilium

Iliofemoral ligament

Greater trochanter

Femur

Ischial Tuberosity Gap

Pubofemoral ligament

Pubis-

Anterior

Iliofemoral ligament

Greater trochanter

Femur

Lesser trochanter

Pubofemoral ligament

Pubis-

Anterior

Iliofemoral ligament

Iliofemoral ligament

Ischiofemoral Ligament

Greater trochanter

Ischial tuberosity

Posterior

Greater trochanter

Ischial tuberosity

Posterior

Femur

Acetabulum

Labrum

Acetabulum

Labrum ligament (cut)

Coxal Joint

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

Lesser Trochanter Hips Human Body

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.

Right Ischial Bursa

Figure 9.22 Treatment of Congenital Hip Dislocation. Infants are sometimes placed in traction to treat this condition.

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