Movements of Diarthroses

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In physical therapy, kinesiology, and other medical and scientific fields, specific terms are used to describe the movements of diarthroses. You will need a command of these terms to understand the muscle actions in chapter 10. In the following discussion, many of them are grouped to describe opposite or contrasting movements.

Flexion, Extension, and Hyperextension

Flexion (figs. 9.9 and 9.10c) is movement that decreases the angle of a joint, usually in a sagittal plane. Examples are bending the elbow or knee and bending the neck to look down at the floor. Bending at the waist, as if taking a bow, is flexion of the spine. Flexion of the shoulder consists of raising the arm from anatomical position in a sagittal plane, as if to point in front of you or toward the ceiling. Flexion of the hip entails raising the thigh, as in a high-stepping marching stance.

Extension is movement that straightens a joint and generally returns a body part to anatomical position— for example, straightening the elbow or knee, raising the head to look directly forward, straightening the waist, or moving the arm back to a position parallel to the trunk.

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Movements Diarthroses
Chapter 9 Joints 303
Diarthroses

Figure 9.9 Joint Flexion and Extension. (a) Flexion of the elbow; (b) extension of the elbow; (c) hyperextension of the wrist; (d) extension of the wrist; (e) flexion of the wrist; (f) flexion of the spine; (g) extension of the spine and flexion of the shoulder; (h) hyperextension of the neck and shoulder.

Figure 9.9 Joint Flexion and Extension. (a) Flexion of the elbow; (b) extension of the elbow; (c) hyperextension of the wrist; (d) extension of the wrist; (e) flexion of the wrist; (f) flexion of the spine; (g) extension of the spine and flexion of the shoulder; (h) hyperextension of the neck and shoulder.

Hyperextension is the extension of a joint beyond 180°. For example, if you extend your arm and hand with the palm down, and then raise the back of your hand as if admiring a new ring, you are hyperextending the wrist. If you look up toward the ceiling, you are hyperextending your neck. If you move your arm to a position posterior to the shoulder, you are hyperextending your shoulder. Each backswing of the lower limb when you are walking hyper-extends your hip joint.

_Think About It_

Some synovial joints have articular surfaces or ligaments that prevent them from being hyperextended. Try hyperextending some of your synovial joints and list a few for which this is impossible.

Abduction and Adduction

Abduction12 (ab-DUC-shun) (fig 9.10) is movement of a body part away from the midsagittal line—for example, raising the arm to one side of the body or standing spread-legged. To abduct the fingers is to spread them apart. Adduction13(ah-DUC-shun) is movement toward the mid-

sagittal line or median axis of the middle digit—that is, returning the body part to anatomical position. Some movements are open to alternative interpretations. Bending the head to one side or bending sideways at the waist may be regarded as abduction or lateral flexion.

Elevation and Depression

Elevation (fig. 9.11a) is movement that raises a bone vertically. The mandible is elevated when biting off a piece of food, and the clavicles are elevated when shrugging the shoulders as if to gesture, "I don't know." The opposite of elevation is depression—lowering the mandible to open the mouth or lowering the shoulders, for example (fig. 9.11b).

Protraction and Retraction

Protraction14 is movement of a bone anteriorly (forward) on a horizontal plane, and retraction15 is movement posteriorly (fig. 9.11c, d). Jutting the jaw outward, hunching the shoulders forward, or thrusting the pelvis forward are examples of protraction. The clavicles are retracted when standing at military attention. Most people have some degree of overbite and must protract the mandible to make the incisors meet when taking a bite of fruit, for example.

  • 2ab = away + duc = to carry, lead ,3ad = toward + duc = to carry, lead
  • 4pro = forward + trac = pull, draw ,5re = back + tract = pull, draw

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9. Joints

Text

© The McGraw-H Companies, 2003

Diarthroses Abduction Limbs

Figure 9.10 Joint Abduction and Adduction. (a) Abduction of the limbs; (b) adduction of the limbs; (c) abduction (lateral flexion) of the spine; (d) abduction of the fingers; (e) adduction of the fingers.

Protraction And Retraction

Figure 9.11 Movements of the Scapulae and Mandible.

  • a) Elevation of the scapulae; (b) depression of the scapulae;
  • c) protraction of the mandible; (d) retraction of the mandible; (e) lateral excursion of the mandible; (f) medial excursion of the mandible.
Mcgraw Hill Circumduction

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Chapter 9 Joints 305

The mandible is then retracted to make the molars meet and grind food between them.

Lateral and Medial Excursion

Biting and chewing food require several movements of the jaw: up and down (elevation-depression), forward and back (protraction-retraction), and side-to-side grinding movements. The last of these are called lateral excursion (sideways movement to the right or left) and medial excursion (movement back to the midline) (fig. 9.11e, f).

Circumduction

Circumduction16 (fig. 9.12a) is movement in which one end of an appendage remains relatively stationary while the other end makes a circular motion. The appendage as a whole thus describes a conical space. For example, if an artist standing at an easel reaches out and draws a circle on the canvas, the shoulder remains stationary while the

16circum = around + duc = to carry, lead

Lateral Standing Whole SpineCircumduction And Rotation

Figure 9.12 Joint Circumduction and Rotation. (a) Circumduction of the upper limb and lateral rotation of the right femur; (b) medial rotation of the right femur; (c) rotation of the spine; (d) lateral rotation of the humerus; (e) medial rotation of the humerus; (f) rotation of the neck (atlantoaxial joint).

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

306 Part Two Support and Movement hand makes a circle. The limb as a whole thus exhibits circumduction. A baseball player winding up for the pitch circumducts the arm in a more extreme "windmill" fashion. Circumduction is actually a sequence of flexion, abduction, extension, and adduction.

Rotation

Rotation is a movement in which a bone turns on its longitudinal axis. Figure 9.12 shows the limb movements that occur in lateral and medial rotation of the femur and humerus. Twisting at the waist is rotation of the trunk. When the head is turned from side to side, the atlas rotates on the axis.

Supination and Pronation

These movements occur in the forearm and foot. Supination17 (SOO-pih-NAY-shun) (fig. 9.13a) of the forearm is rotation so that the palm faces forward or upward; in anatomical position, the forearm is supine. Pronation18 (fig. 9.13b) is rotation of the forearm so that the palm faces toward the rear or downward. As an aid to memory, think of it this way: You are prone to stand in the most comfortable position, which is with the palm pronated. If you were holding a bowl of soup in your hand, your forearm would have to be supinated. These movements are achieved with muscles discussed in chapter 10. The supinator muscle is the most powerful, and supination is the sort of movement you would usually make with the right hand to turn a doorknob clockwise or drive a screw into a piece of wood.

To supinate the foot is to invert and abduct it, raising the medial edge. To pronate the foot is to evert and abduct it, raising the lateral edge.

Opposition and Reposition

Opposition19 is movement of the thumb to approach or touch the fingertips, and reposition20 is its movement back to anatomical position, parallel to the index finger (fig. 9.13 c, d). Opposition is the movement that enables the hand to grasp objects and is the single most important hand function.

Dorsiflexion and Plantar Flexion

These movements are limited to the foot. Dorsiflexion (DOR-sih-FLEC-shun) is a movement in which the toes are raised (as one might do to apply toenail polish) (fig. 9.14a).

17supin = to lay back

18pron = to bend forward

Pronation Hand

Figure 9.13 Joint Movements of the Forearm and Hand.

(a) Supination of the forearm; (b) pronation of the forearm; (c) opposition of the thumb; (d) reposition of the thumb.

Figure 9.13 Joint Movements of the Forearm and Hand.

(a) Supination of the forearm; (b) pronation of the forearm; (c) opposition of the thumb; (d) reposition of the thumb.

The foot is dorsiflexed in each step you take as your foot comes forward. Dorsiflexion prevents your toes from scraping on the ground and results in a "heel strike" when that foot touches down in front of you. Plantar (PLAN-tur) flexion is extension of the foot so that the toes point downward, as in standing on tiptoe or pressing the gas pedal of a car (fig. 9.14c). This motion also produces the "toe-off" in each step you take, as the heel of the foot behind you lifts off the ground.

Inversion and Eversion

These movements are also unique to the feet (fig. 9.14d, e). Inversion21 is a movement in which the soles are

21 in = inward + version = turning

Saladin: Anatomy & I 9. Joints I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition sS

Figure 9.14 Joint Movements of the Foot. (a) Dorsiflexion; (b) extension; (c) plantar flexion; (d) inversion; (e) eversion.

turned medially;

eversion is a turning of the soles to face laterally. Inversion and eversion are common in fast sports such as tennis and football and often result in ankle sprains. These terms also refer to congenital deformities of the feet, which are often corrected by orthopedic shoes or braces.

_Think About It_

A chimpanzee sitting on the ground reaches out and grasps an object between its fingertips. Then it raises its hand to its face and turns the object to examine it. List the movements that would occur at its diarthroses and identify the joint at which each one would occur.

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  • Albertina
    What is pronation movement with the hand?
    3 years ago

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