The muscles of this chapter are involved with motions of the forearm (radius and ulna) at the radioulnar joints, the hand at the wrist (radiocarpal) joint, and the fingers at the metacarpophalangeal (MCP) and/or the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints; the thumb also moves at the first carpometacarpal (CMC) (saddle) joint.

Forearm muscles are usually divided into an anterior flexor compartment and a posterior extensor compartment. The flexor compartment has three layers: superficial, intermediate, and deep. The extensor compartment has two layers: superficial and deep. A third group, called the radial group (also known as the wad of three), is sometimes designated. It consists of the brachioradialis of the anterior compartment and the extensors carpi radialis longus and brevis of the posterior compartment.

Two other structures of importance in the forearm are the common flexor tendon and the common extensor tendon. The common flexor tendon attaches to the medial epicondyle of the humerus. Five muscles attach into the common flexor tendon: (1) flexor carpi radialis, (2) palmaris longus, (3) flexor carpi ulnaris, (4) pronator teres, and (5) flexor digitorum superficialis. The common extensor tendon attaches to the lateral epicondyle of the humerus. Four muscles attach into the common extensor tendon: (1) extensor carpi radialis brevis, (2) extensor digitorum, (3) extensor digiti minimi, and (4) extensor carpi ulnaris.

Muscles that move the fingers are often divided into extrinsic and intrinsic hand/finger muscles. Intrinsic hand muscles are wholly located within the hand; in other words, they originate and insert within the hand. Intrinsic muscles on the palmar side of the hand can be divided into three groups: (1) thenar eminence, (2) hypothenar eminence, and (3) central compartment.

Extrinsic finger muscles have their origin (proximal attachment) outside of the hand, in the forearm or arm. Because they also cross the wrist and/or elbow joints, they can also move those joints.

A structure of importance in the hand is the dorsal digital expansion. The dorsal digital expansion is a fibrous expansion of the extensor digitorum and extensor pollicis longus muscles’ distal tendons on the dorsal side of the fingers (digits).

As a general rule, muscles that move the elbow joint have their origin (proximal attachment) on the arm (humerus) and their insertion (distal attachment) on the forearm (radius or ulna) or hand. Muscles that pronate or supinate the forearm usually have their origin (proximal attachment) on the radius and their insertion (distal attachment) on the ulna. Muscles that move the wrist joint usually have their origin (proximal attachment) on the arm or forearm and their insertion (distal attachment) on the hand. Finger muscles may be extrinsic or intrinsic as previously discussed.

As a rule, flexor and pronator muscles attach to the medial epicondyle of the humerus via the common flexor tendon.

As a rule, extensor and supinator muscles attach to the lateral epicondyle of the humerus via the common extensor tendon.

The companion CD at the back of this book allows you to examine the muscles of this body region, layer by layer, and individual muscle palpation technique videos are available in the Chapter 7 folder on Evolve.

OVERVIEW OF FUNCTION: MUSCLES OF THE ELBOW AND RADIOULNAR JOINTS

The following general rules regarding actions can be stated for the functional groups of the muscles of the elbow and radioulnar joints.

If a muscle crosses the elbow joint anteriorly with a vertical direction to its fibers, it can flex the forearm at the elbow joint by moving the anterior surface of the forearm toward the anterior surface of the arm.

If a muscle crosses the elbow joint posteriorly with a vertical direction to its fibers, it can extend the forearm at the elbow joint by moving the posterior surface of the forearm toward the posterior surface of the arm.

Reverse actions at the elbow joint involve moving the arm toward the forearm at the elbow joint. This movement usually occurs when the hand (and therefore the forearm) is fixed by holding onto an immovable object.*

ent If a muscle crosses the radioulnar joints anteriorly with a horizontal orientation to its fibers, it will pronate the forearm at the radioulnar joints by crossing the radius over the ulna.

If a muscle crosses the radioulnar joints posteriorly with a horizontal direction to its fibers, it will supinate the forearm at the radioulnar joints by moving the radius to be parallel with the ulna.

Reverse actions of these standard mover actions at the radioulnar joints involve moving the ulna toward the radius at the radioulnar joints. This movement usually occurs when the hand (and therefore the radius) is fixed by holding onto an immovable object.*

OVERVIEW OF FUNCTION: MUSCLES OF THE WRIST JOINT

The following general rules regarding actions can be stated for the functional groups of the muscles of the wrist joint:

If a muscle crosses the wrist joint anteriorly with a vertical direction to its fibers, it can flex the hand at the wrist joint by moving the palmar (anterior) surface of the hand toward the anterior surface of the forearm.

If a muscle crosses the wrist joint posteriorly with a vertical direction to its fibers, it can extend the hand at the wrist joint by moving the dorsal (posterior) surface of the hand toward the posterior surface of the forearm.

If a muscle crosses the wrist joint on the radial side (laterally) with a vertical direction to its fibers, it can radially deviate (abduct) the hand at the wrist joint by moving the radial side of the hand toward the radial side of the forearm.

If a muscle crosses the wrist joint on the ulnar side (medially) with a vertical direction to its fibers, it can ulnar deviate (adduct) the hand at the wrist joint by moving the ulnar side of the hand toward the ulnar side of the forearm.

Reverse actions of these standard mover actions involve the forearm being moved toward the hand at the wrist joint. These reverse actions usually occur when the hand is fixed, such as when holding onto an immovable object.*

OVERVIEW OF FUNCTION: MUSCLES OF THE FINGERS

The following general rules regarding actions can be stated for the functional groups of finger muscles:

Fingers two through five can move at three joints: (1) MCP, (2) PIP, and (3) DIP joints. If a muscle crosses only the MCP joint, it can move the finger only at the MCP joint. If the muscle crosses the MCP and PIP joints, it can move the finger at both of these joints. If the muscle crosses the MCP, PIP, and DIP joints, it can move the finger at all three joints.

Note: The little finger can also move at the CMC joint.

The thumb (finger one) can move at three joints: the CMC, MCP, and interphalangeal (IP) joints. Similarly, a muscle can only move the thumb at a joint or joints that it crosses.

If a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the anterior side, it can flex the finger at the joint(s) crossed; if a muscle crosses the MCP, PIP, or DIP joints of fingers two through five on the posterior side, it can extend the finger at the joint(s) crossed.

If a muscle crosses the MCP joint of fingers two, four, or five on the side that faces the middle finger, it can adduct the finger at the MCP joint. If a muscle crosses the MCP joint of fingers two, three, or four on the side that is away from the middle finger side, it can abduct the finger at the MCP joint (the middle finger abducts in both directions—radial and ulnar).

Muscles that cross the CMC, MCP, and IP joints of the thumb on the medial side can flex the thumb at the joint(s) crossed. Muscles that cross the CMC, MCP, and IP joints of the thumb on the lateral side can extend the thumb at the joint(s) crossed.

Muscles that cross the CMC joint of the thumb on the anterior side can abduct the thumb at the CMC joint. Muscles that cross the CMC joint of the thumb on the posterior side can adduct the thumb at the CMC joint.

Reverse actions involve the proximal attachment moving toward the distal attachment. This movement occurs when the fingers are holding onto a fixed, immovable object.*

Notes

FOREARM AND HAND: Wrist Flexor Group

Flexor Carpi Radialis; Palmaris Longus; Flexor Carpi Ulnaris

Pronunciation FLEKS-or KAR-pie RAY-dee-A-lis • pall-MA-ris LONG-us • FLEKS-or KAR-pie ul-NA-ris

The wrist flexor group is composed of three muscles that all originate (have their proximal attachment) on the medial epicondyle of the humerus via the common flexor tendon. They all cross the wrist joint anteriorly; therefore they can all flex the hand at the wrist joint, hence the name of the group. These muscles are the flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. All three muscles of the wrist flexor group are superficial in the anterior forearm. At the wrist joint, the palmaris longus crosses dead center; the flexor carpi radialis crosses slightly to the radial (lateral) side; and the flexor carpi ulnaris crosses far to the ulnar (medial) side (Figure 7-7). In addition to the humeral attachment, the flexor carpi ulnaris also has an ulnar attachment. The humeral head is much thicker; the ulnar head is extremely thin.

FIGURE 7-7 Anterior view of the right wrist flexor group of muscles. O, Origin; I, insertion.

WHAT’S IN A NAME?

flexor carpi radialis, tells us that this muscle flexes and radially deviates (abducts); carpi tells us that these actions occur at the wrist joint.

The name, flexor carpi ulnaris, tells us that this muscle flexes and ulnar deviates (adducts) the wrist joint.

The name, palmaris longus, tells us that this muscle attaches into the palm of the hand and is long (longer than the palmaris brevis).

*Derivation:

flexor: L. muscle that flexes a body part

radialis: L. refers to the radial side (of the forearm)

ulnaris: L. refers to the ulnar side (of the forearm)

palmaris: L. refers to the palm

longus: L. longer

carpi: L. of the wrist

ATTACHMENTS

Flexor Carpi Radialis

The flexor carpi radialis is superficial in the anterior forearm and located between the pronator teres and the palmaris longus.

Origin (Proximal Attachment)

Medial epicondyle of the humerus via the common flexor tendon

Insertion (Distal Attachment)

Anterior hand on the radial side

Palmaris Longus

The palmaris longus is superficial in the anterior forearm and located between the flexor carpi radialis and the flexor carpi ulnaris.

Origin (Proximal Attachment)

Medial epicondyle of the humerus via the common flexor tendon

Insertion (Distal Attachment)

Palm of the hand

Flexor Carpi Ulnaris

The flexor carpi ulnaris is superficial in the anterior forearm and located medial to the palmaris longus.

Origin (Proximal Attachment)

Medial epicondyle of the humerus via the common flexor tendon, and the ulna

Insertion (Distal Attachment)

Anterior hand on the ulnar side

ACTIONS

All three muscles of the wrist flexor group flex the hand at the wrist joint.

The flexor carpi radialis also radially deviates the hand at the wrist joint.

The flexor carpi ulnaris also ulnar deviates the hand at the wrist joint.

STABILIZATION

As a group, the wrist flexor muscles stabilize the wrist, elbow, and radioulnar joints.

Stabilization Function Note: The flexor carpi ulnaris also stabilizes the pisiform bone of the carpal group when the abductor digiti minimi manus (intrinsic muscle of the hand) contracts, so that the abductor digiti minimi manus can efficiently abduct the little finger.

INNERVATION

Median and ulnar nerves

Note: The median nerve innervates the flexor carpi radialis and palmaris longus; the ulnar nerve innervates the flexor carpi ulnaris.

PALPATION

1. The client is seated with the arm relaxed. The forearm is flexed at the elbow joint and is fully supinated and resting on the client’s thigh. Place your support/resistance hand on the client’s hand, just proximal to the fingers.

2. Resist the client from flexing the hand at the wrist joint (be sure that you do not contact the fingers when offering resistance), and look for the distal tendons of all three wrist flexors to become visible. If they do not become visible, then they should be palpable by strumming perpendicularly across them. The flexor carpi ulnaris is usually the least visible.

3. Begin by palpating the flexor carpi radialis by strumming horizontally across it (Figure 7-8). Then palpate the palmaris longus and flexor carpi ulnaris in a similar manner.

4. Continue palpating each of these muscles proximally to the medial epicondyle by strumming across its fibers.

Note: The flexor carpi radialis can be palpated with resisted radial deviation of the hand at the wrist joint; similarly, the flexor carpi ulnaris can be palpated with ulnar deviation. The palmaris longus can be palpated by asking the client to “cup the hand” (Figure 7-9).

FIGURE 7-9 Palpation of the muscles of the right wrist flexor group. A, Palpation of the flexor carpi radialis as the client radially deviates the hand against resistance. The palmaris longus has been ghosted in. B, Palpation of the flexor carpi ulnaris as the client ulnar deviates the hand against resistance (the palmaris longus has been ghosted in). C, The palmaris longus is engaged when the client cups his hand.

TREATMENT CONSIDERATIONS

Overuse of the wrist flexor group musculature can cause irritation and/or inflammation of the medial epicondyle and/or the common flexor tendon. This condition is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow

In many individuals, the palmaris longus is bilaterally or unilaterally absent.

The ulnar nerve passes between the two heads of the flexor carpi ulnaris. Compression of the ulnar nerve between the two heads of the flexor carpi ulnaris is called cubital tunnel syndrome.

FOREARM AND HAND: PRONATOR GROUP

Pronator Teres; Pronator Quadratus

Pronunciation pro-NAY-tor TE-reez • pro-NAY-tor kwod-RAY-tus

The pronator teres and pronator quadratus muscles are located in the anterior forearm. The pronator teres is superficial in the proximal forearm; the pronator quadratus is very deep in the distal forearm. The pronator teres has two heads—a large, superficial humeral head and a small, deep ulnar head (Figure 7-10).

FIGURE 7-10 Anterior view. The supinator and brachialis (cut) have been ghosted in. O, Origin; I, insertion.

WHAT’S IN A NAME?

pronator, tells us that these muscles pronate the forearm. Teres refers to being round in shape; quadratus refers to being square in shape.

*Derivation:

pronator: L. muscle that pronates a body part

teres: L. round

quadratus: L. squared

ATTACHMENTS

Pronator Teres

Origin (Proximal Attachment)

Humeral head: Medial epicondyle of the humerus via the common flexor tendon

Ulnar head: Coronoid process of the ulna

Insertion (Distal Attachment)

Lateral radius

Pronator Quadratus

Origin (Proximal Attachment)

Anterior distal ulna

Insertion (Distal Attachment)

Anterior distal radius

ACTIONS

Stabilization Function Note: The pronator quadratus is especially important for preventing the separation of the distal radius and ulna.

INNERVATION

Median nerve

PALPATION

Pronator Teres

1. The client is seated with the arm relaxed and the forearm flexed at the elbow joint and in a position that is halfway between full pronation and full supination; the forearm is resting on the client’s thigh. Place your palpating thumb or finger pads on the proximal anterior forearm, and gently but firmly grasp the client’s distal forearm just proximal to the wrist joint with your support/resistance hand.

2. With moderate force, resist the client from pronating the forearm at the radioulnar joints and feel for the contraction of the pronator teres (Figure 7-11).

3. Strumming perpendicular to the fibers, palpate from attachment to attachment. Be sure to strum across the entire muscle belly.

Pronator Quadratus

1. The client is seated or supine with the forearm fully supinated. Place your palpating finger pads on the distal forearm, just proximal to the wrist.

2. Ask the client to pronate the forearm actively at the radioulnar joints, and feel for the contraction of the pronator quadratus. Resistance can be added if necessary (Figure 7-12).

FIGURE 7-12 View of the right pronator quadratus being palpated as pronation of the forearm at the radioulnar joints is resisted.

Note: The pronator quadratus is deep and can be difficult to palpate and discern. Further, the median and ulnar nerves and radial and ulnar arteries are located in the anterior wrist; prudence must be exercised when palpating deeply here.

TREATMENT CONSIDERATIONS

The median nerve courses between the humeral head and the ulnar head of the pronator teres, making it a possible entrapment site. When the median nerve is entrapped here, it is termed pronator teres syndrome and may mimic symptoms of carpal tunnel syndrome or a pathologic cervical disc.

Overuse of the pronator teres can cause irritation and/or inflammation of the medial epicondyle and/or the common flexor tendon. This condition is known as medial epicondylitis, medial epicondylosis, or golfer’s elbow.

FOREARM AND HAND

Brachioradialis

Pronunciation BRAY-key-o-RAY-dee-AL-is

The brachioradialis is superficial for its entire course (except for a small part of its distal tendon that is deep to two small muscles of the thumb whose bellies are located deep in the posterior forearm). The brachioradialis is located in the anterior forearm on the radial (lateral) side. Because it is on the radial side, it is considered to be part of the “radial group,” along with the extensor carpi radialis longus and extensor carpi radialis brevis (Figure 7-13).

FIGURE 7-13 Anterior view of the right brachioradialis. The brachialis has been ghosted in. O, Origin; I, insertion.

WHAT’S IN A NAME?

brachioradialis, tells us that this muscle attaches onto the brachium (the arm) and the radius.

* Derivation:

brachio: L. refers to the arm

radialis: L. refers to the radius

ATTACHMENTS

Origin (Proximal Attachment)

Lateral supracondylar ridge of the humerus

Insertion (Distal Attachment)

Styloid process of the radius

ACTIONS

The brachioradialis moves the forearm at the elbow and radioulnar joints.

Flexes the forearm at the elbow joint.

Supinates the forearm at the radioulnar joints.

Pronates the forearm at the radioulnar joints.

Action Note: If the forearm is fully pronated, the brachioradialis can supinate it to a position that is halfway between full pronation and full supination. If the forearm is fully supinated, the brachioradialis can pronate it to a position that is halfway between full pronation and full supination.

STABILIZATION

Stabilizes the elbow and radioulnar joints.

INNERVATION

Radial nerve

PALPATION

1. The client is seated with the arm relaxed and the forearm flexed at the elbow joint and in a position that is halfway between full pronation and full supination; the forearm is resting on the client’s thigh. Place your support/resistance hand on the client’s anterior distal forearm, just proximal to the wrist joint.

2. Ask the client to try to flex the forearm with moderate force against your resistance. First look for the contraction of the brachioradialis and then feel for its contraction at the proximal anterolateral forearm (Figure 7-14).

3. Strumming perpendicular to the fibers, palpate proximally to the lateral supracondylar ridge of the humerus and then distally to the styloid process of the radius.

Note: Contacting and adding resistance to the distal forearm, not the hand, is extremely important. If resistance is added to the hand, then the adjacent extensor carpi radialis longus will engage, making it difficult to discern the brachioradialis from this muscle.

TREATMENT CONSIDERATIONS

The brachioradialis is one of the three Bs of elbow joint flexion: (1) biceps brachii, (2) brachialis, and (3) brachioradialis. The biceps brachii flexes best when the forearm is fully supinated; the brachialis flexes best when the forearm is fully pronated; the brachioradialis flexes best when the forearm is halfway between fully supinated and fully pronated.

The brachioradialis is sometimes nicknamed the hitchhiker muscle for the characteristic action of flexing the forearm in a position halfway between full pronation and full supination (with the thumb up) when hitchhiking. (Keep in mind that the brachioradialis has no action on the thumb itself.)

FOREARM AND HAND: Flexors Digitorum and Pollicis Group

Flexor Digitorum Superficialis: Flexor Digitorum Profundus; Flexor Pollicis Longus

Pronunciation FLEKS-or dij-i-TOE-rum SOO-per-fish-ee-A-lis •

FLEKS-or dij-i-TOE-rum pro-FUN-dus • FLEKS-or POL-i-sis LONG-us

The flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus are all long, extrinsic flexors of the fingers. Both flexor digitorum muscles flex fingers 2 through 5; and the flexor pollicis muscle flexes the thumb (finger 1). These muscles are considered to be long extrinsic finger muscles because they originate (have their proximal attachment) outside of the hand. The flexor digitorum superficialis is in the intermediate layer of anterior forearm muscles, directly deep to the muscles of the wrist flexor group. The flexor digitorum profundus and flexor pollicis longus are in the deep layer of the anterior forearm, deep to the flexor digitorum superficialis (Figure 7-15).

FIGURE 7-15 A, Anterior view of the right flexor digitorum superficialis. B, Anterior view of the right flexor digitorum profundus. C, Anterior view of the right flexor pollicis longus. The distal end of the brachialis has been ghosted in all three figures. The pronator quadratus has been ghosted in B and C. O, Origin; I, insertion.

WHAT’S IN A NAME?

flexor digitorum superficialis, tells us that this muscle flexes the digits (i.e., fingers) and is superficial to the flexor digitorum profundus.

The name, flexor digitorum profundus, tells us that this muscle flexes the digits (i.e., fingers) and is deep to the flexor digitorum superficialis.