CHAPTER 4 Muscles of the Shoulder Girdle Joints
Right Lateral View of the Muscles of the Shoulder Girdle and Neck Region
101
4
Semispinalis
capitis
Splenius
capitis
Hyoid bone
Levator scapulae
Sternocleidomastoid
Scalenes
Trapezius
Omohyoid
Clavicle
Acromion process
of scapula
Pectoralis major
Deltoid
Scapula
Serratus anterior
Figure 4-3
CHAPTER 4 Muscles of the Shoulder Girdle Joints
105
Rhomboids Major and Minor
The name, rhomboids, tells us that these muscles have the geometric shape of a rhombus (a parallelogram or diamond shape). Major
tells us that the rhomboid major is the larger muscle of the two;
minor tells us that the rhomboid minor is smaller.
rhomb:
Gr. rhombos (the
geometric shape).
oid:
Gr. shape, resemblance.
major:
L. larger.
minor:
L. smaller.
Pronunciation ROM-boyd, MAY-jor, MY-nor
Derivation
4
Levator scapulae
Rhomboid minor
Rhomboid major
■ ATTACHMENTS
THE RHOMBOIDS: Spinous Processes of C7-T5
MINOR: spinous processes of C7-T1 and the inferior
nuchal ligament
MAJOR: spinous processes of T2-T5
to the
THE RHOMBOIDS: Medial Border of the Scapula From
the Root of the Spine to the Inferior Angle of the Scapula
MINOR: at the root of the spine of the scapula
MAJOR: between the root of the spine and the inferior
Figure 4-5 Posterior view of the right rhomboids major and minor.
The levator scapulae has been ghosted in.
angle of the scapula
■ FUNCTIONS
CONCENTRIC (SHORTENING) MOVER ACTIONS
Standard Mover Actions
Reverse Mover Actions
ScC joint
trunk at the spinal joints
ScC joint
3. Downwardly rotates the
scapula at the ScC joint
4. Medially tilts the scapula at
the ScC joint
joints
1. Retracts the scapula at the 1. Contralaterally rotates the
2. Elevates the scapula at the 2. Extends the trunk at the spinal
3. Contralaterally rotates the
trunk at the spinal joints
ScC joint = scapulocostal joint
Standard Mover Action Notes
• The rhomboids attach from the spine medially, to the scapula
laterally (with their fibers running somewhat horizontally).
When the rhomboids contract, they pull the scapula medially toward the spine; therefore the rhomboids retract
(adduct) the scapula at the scapulocostal joint. (action 1)
• The rhomboids attach from the spine superiorly, to the
scapula inferiorly (with their fibers running somewhat vertically). When the rhomboids contract, they pull the scapula
superiorly toward the spine; therefore the rhomboids elevate
the scapula at the scapulocostal joint. (action 2)
• When the rhomboids contract, they pull on the scapula,
causing the inferior angle of the scapula to swing up toward
the spine. This will cause the glenoid fossa to orient downward; therefore the rhomboids downwardly rotate the
scapula at the scapulocostal joint. The rhomboid major is
more powerful than the rhomboid minor at downward
rotation because its attachment on the scapula is more inferior. From there it has better leverage to rotate the scapula
because it attaches farther from the axis of scapular rotation.
(action 3)
• Downward rotation of the scapula at the scapulocostal joint
is the best joint action to engage and palpate the rhomboids.
(action 3)
• Medial tilt is a motion of the scapula that brings its medial
border back against the body wall. In anatomic position, the
scapula should be fully medially tilted. The action of medial
tilt of the scapula is particularly important when the scapula
is protracted because the scapula tends to laterally tilt (i.e.,
wing out) when it protracts. Therefore muscles that medially
tilt the scapula keep the scapula from laterally tilting, or
winging out. (action 4)
Reverse Mover Action Notes
• When the scapula is fixed and the rhomboids contract, they
pull the spinous processes of the vertebrae toward the
scapula. This will cause the anterior bodies of these vertebrae
106
PART 2 The Skeletal Muscles of the Upper Extremity
4
Rhomboids Major and Minor—cont’d
to rotate to the opposite side of the body. Therefore the
rhomboids can contralaterally rotate the trunk at the spinal
joints. (reverse actions 1, 3)
• The rhomboids cross the spinal joints posteriorly with a
vertical direction to their fibers. If the scapula is fixed, the
spinal attachment is pulled inferiorly toward the scapula.
Therefore, the rhomboids can extend the trunk at the spinal
joints. (reverse action 2)
■ RELATIONSHIP TO OTHER
STRUCTURES
The rhomboids are deep to the trapezius.
The rhomboid minor is directly superior to the rhomboid
major.
The rhomboid minor attaches onto the scapula, inferior to
the levator scapulae’s attachment onto the scapula.
Deep to the rhomboids are the splenius capitis, the splenius
Eccentric Antagonist Functions
1. Restrains/slows scapular protraction, depression, upward
rotation, and lateral tilt
2. Restrains/slows flexion and ipsilateral rotation of the trunk
cervicis, the serratus posterior superior, and the erector
spinae and transversospinalis groups.
The rhomboids are located within the spiral line and deep
back arm line myofascial meridians.
■ MISCELLANEOUS
Isometric Stabilization Functions
1. Stabilizes the scapula
2. Stabilizes C7-T5 vertebrae
INNERVATION
The Dorsal Scapular Nerve
C4, C5
ARTERIAL SUPPLY
The Dorsal Scapular Artery (a branch of the Subclavian Artery)
,
P A LPATION
1. With the client seated or prone and the hand placed in the small
of the back, place palpating hand between the scapula (at a
level that is between the inferior angle and the root of the spine
of the scapula) and the spine.
2. Ask the client to move the hand away from the back and feel
for the contraction of the rhomboids.
3. Palpate the entirety of the rhomboids.
1. The rhomboids major and minor are considered together
because they have identical fiber direction and therefore
identical lines of pull and identical actions (except for the
greater downward rotation force of the rhomboid major).
2. Sometimes there is a small interval of space between the two
rhomboids, but often there is not. These two muscles may
even blend together.
3. The rhomboids often blend into the serratus anterior on the
anterior side of the scapula.
4. The rhomboid muscles are sometimes called the Christmas
tree muscles. When you look at the rhomboids bilaterally
with the spinal column between them, they look like a
Christmas tree in shape.
5. Rounded shoulders is a common postural condition in which
the scapulae are protracted (abducted) and depressed at the
scapulocostal joints and the humeri are medially rotated at
the shoulder joints. Given the rhomboids’ actions of both
retraction and elevation of the scapulae, when the rhomboid
muscles are weak, they can contribute to this condition
because they are unable to efficiently oppose protraction and
depression of the scapulae. This is especially true if the protractors and/or depressors of the scapulae (often the pectoralis minor and major muscles) are tight.
CHAPTER 5 Muscles of the Glenohumeral Joint
121
Deltoid
The name, deltoid, tells us that this muscle has a triangular shape
similar to the Greek letter delta (Δ).
■ FUNCTIONS
CONCENTRIC (SHORTENING) MOVER ACTIONS
Derivation
delta: Gr. the letter delta (Δ).
Standard Mover Actions
Reverse Mover Actions
Pronunciation
DEL-toid
joint (entire muscle)
scapula at the GH and
scapulocostal joints
2. Ipsilaterally rotates the trunk
oid: Gr. resemblance.
■ ATTACHMENTS
Lateral Clavicle, Acromion Process, and the Spine of the
Scapula
the lateral 1 3 of the clavicle
to the
Deltoid Tuberosity of the Humerus
1. Abducts the arm at the GH 1. Downwardly rotates the
2. Flexes the arm at the GH
joint (anterior deltoid)
3. Medially rotates the arm at
the GH joint (anterior deltoid)
4. Horizontally flexes the arm
at the GH joint (anterior deltoid)
5. Extends the arm at the GH
joint (posterior deltoid)
6. Laterally rotates the arm at
the GH joint (posterior deltoid)
7. Horizontally extends the
arm at the GH joint (posterior
deltoid)
3. Contralaterally rotates the
trunk
GH joint = glenohumeral joint
A
B
C
Figure 5-6 The right deltoid. A, Lateral view. The proximal end of the brachialis has been ghosted
in. B, Anterior view. The proximal ends of the pectoralis major and brachialis have been ghosted in.
C, Posterior view. The proximal end of the triceps brachii has been ghosted in.
5
122
PART 2 The Skeletal Muscles of the Upper Extremity
Deltoid—cont’d
Standard Mover Action Notes
5
• The deltoid crosses over the top of the GH joint on the
lateral side (with its fibers running vertically in the frontal
plane); therefore it abducts the arm at the GH joint. The
anterior and posterior parts of the deltoid can abduct the
arm at the GH joint, but the fibers of the middle deltoid
have the best line of pull for this action. (action 1)
• Although the deltoid can abduct the arm at the GH joint
throughout its entire range of motion, the deltoid’s activity
is strongest between 90 degrees and 120 degrees. (action 1)
• The lowest fibers of the anterior deltoid and posterior deltoid
can adduct the arm at the GH joint because they pass inferior to the axis of motion of the GH joint. (action 1)
• The anterior deltoid crosses the GH joint anteriorly (with
its fibers running vertically in the sagittal plane); therefore
it flexes the arm at the GH joint. The anterior deltoid is
considered to be the prime mover of flexion of the arm at
the GH joint. (action 2)
• The middle deltoid also has a component of flexion of the
arm because the scapula is oriented approximately 35 degrees
off the frontal plane toward the sagittal plane. (action 2)
• The anterior deltoid crosses the GH joint anteriorly from
medial on the clavicle to more lateral on the humerus (with
its fibers running somewhat horizontally in the transverse
plane). However, it does not attach onto the first aspect of
the humerus that it reaches, but rather it wraps around the
humerus to attach onto the deltoid tuberosity. Therefore
when the anterior deltoid contracts, the anterior surface of
the humerus rotates medially. This movement is called
medial rotation of the arm at the GH joint. (action 3)
• When the arm is first abducted 90 degrees, the fibers of the
anterior deltoid are lined up horizontally in front of the GH
joint. When the humeral attachment is pulled toward the
clavicular attachment, the arm is moved horizontally and
anteriorly, toward the midline of the body; this motion is
called horizontal flexion (or horizontal adduction) of the
arm at the GH joint. (action 4)
• The anterior deltoid is a powerful horizontal flexor of the
arm at the GH joint. In fact, this is the best action to engage
and isolate the anterior deltoid from the middle and posterior deltoid when palpating it. (action 4)
• The posterior deltoid crosses the GH joint posteriorly (with
its fibers running vertically in the sagittal plane); therefore
it extends the arm at the GH joint. (action 5)
• The posterior deltoid crosses the GH joint posteriorly from
medial on the scapula to more lateral on the humerus (with
its fibers running somewhat horizontally in the transverse
plane). However, it does not attach onto the first aspect of
the humerus that it reaches, but rather it wraps around the
humerus to attach onto the deltoid tuberosity. Therefore
when the posterior deltoid contracts, the anterior surface of
the humerus rotates laterally. This movement is called lateral
rotation of the arm at the GH joint. (action 6)
• When the arm is first abducted 90 degrees, the fibers of the
posterior deltoid are lined up horizontally in back of the GH
joint. When the humeral attachment is pulled toward the
attachment on the spine of the scapula, the arm is moved
horizontally and posteriorly, away from the midline of the
body; this motion is called horizontal extension (or horizontal abduction) of the arm at the GH joint. (action 7)
• The posterior deltoid is a powerful horizontal extensor of the
arm at the GH joint. In fact, this is the best action to engage
and isolate the posterior deltoid from the middle and anterior deltoid when palpating it. (action 7)
Reverse Mover Action Notes
• When the arm is fixed and the deltoid contracts, the deltoid
pulls directly on the scapula (and indirectly on the scapula
by pulling on the lateral clavicle), pulling the acromion
process inferiorly toward the humerus. This causes the inferior angle of the scapula to swing up toward the vertebral
column and causes the glenoid fossa to orient downward.
Therefore the deltoid downwardly rotates the scapula relative
to the humerus at the GH joint and relative to the rib cage
at the scapulocostal joint. (reverse action 1)
• The reverse action of downward rotation of the scapula by
the deltoid is extremely important. If this action is not
opposed by an upward rotator muscle (usually the upper
trapezius) when the deltoid contracts to abduct the humerus,
the humeral head and acromion process of the scapula will
approximate each other, pinching the rotator cuff tendon
and subacromial bursa between them. (reverse action 1)
• If the arm is fixed and the anterior deltoid pulls on the clavicle,
the clavicle would normally be moved at the sternoclavicular
joint (into depression, downward rotation, and protraction).
However, if the clavicle and scapula are fixed to the trunk, the
trunk will be pulled with the clavicle and scapula and will be
rotated such that it faces the same side of the body on which
the anterior deltoid is located. This action may be called ipsilateral rotation of the trunk at the GH joint (in reality, it is a
scapular motion relative to the humerus at the GH joint and
the trunk, being fixed to the clavicle and scapula, goes along
for the ride, rotating such that it comes to face the same side
of the body). (reverse action 2)
• If the arm is fixed and the posterior deltoid pulls on the
scapula, the scapula would normally be moved at the GH
and scapulocostal joints (into downward rotation and downward tilt). However, if the scapula is fixed to the trunk, the
trunk will be pulled with the scapula and will be rotated
such that it faces the opposite side of the body from where
the posterior deltoid is located. This action may be called
contralateral rotation of the trunk at the GH joint (in reality,
it is a scapular motion relative to the humerus at the GH
joint; and the trunk, being fixed to the scapula, goes along
for the ride, rotating such that it comes to face the other side
of the body). (reverse action 3)
CHAPTER 5 Muscles of the Glenohumeral Joint
123
Deltoid—cont’d
Eccentric Antagonist Functions
1. Restrains/slows arm adduction, extension, horizontal extension, flexion, horizontal flexion, lateral rotation, and medial
rotation
2. Restrains/slows contralateral rotation and ipsilateral rotation
of the trunk
3. Restrains/slows clavicular elevation, upward rotation, and
retraction
4. Restrains/slows scapular upward rotation and upward tilt
Eccentric Antagonist Function Note
• Upward tilt of the scapula is a motion in which the inferior
angle of the scapula lifts away from the rib cage wall.
■ RELATIONSHIP TO OTHER
STRUCTURES
The deltoid is superficial and found at the anterior, lateral,
Isometric Stabilization Functions
1. Stabilizes the GH joint
2. Stabilizes the scapula and clavicle
and posterior shoulder. It gives the shoulder its characteristic
shape.
The anterior deltoid lies next to the clavicular head of the
pectoralis major.
Inferior to the posterior deltoid are the infraspinatus, the
teres minor, the teres major, and the triceps brachii.
The following muscles all have tendons that are deep to the
deltoid: the pectoralis minor, the coracobrachialis, and the
short head of the biceps brachii (all attaching to the coracoid
process of the scapula); the supraspinatus, the infraspinatus,
the teres minor, and the subscapularis (rotator cuff muscles
attaching to the greater and lesser tubercles of the humerus);
and the pectoralis major, the long head of the biceps brachii,
and the long and lateral heads of the triceps brachii.
The deltoid is located within the superficial back arm line
myofascial meridian.
■ MISCELLANEOUS
INNERVATION
The Axillary Nerve
C5, C6
ARTERIAL SUPPLY
The
Anterior and Posterior Circumflex Humeral Arteries
(branches of the Axillary Artery)
and the Pectoral and Deltoid branches of the Thoracoacromial Trunk (a branch of the Axillary Artery)
,
P A L PATION
1. With the client seated, place palpating hand just distal to the
acromion process of the scapula.
2. Have the client abduct the arm at the glenohumeral joint and
feel for the contraction of the deltoid. Resistance can be added.
3. Continue palpating the deltoid anteriorly for the anterior fibers
and posteriorly for the posterior fibers. Palpate all fibers distally
to the deltoid tuberosity of the humerus.
4. Note: Horizontal flexion can be used for the anterior fibers;
horizontal extension can be used for the posterior fibers.
1. The deltoid is considered to have three parts: anterior,
middle, and posterior.
2. The anterior deltoid crosses the glenohumeral joint anteriorly and attaches to the lateral clavicle proximally. The
middle deltoid crosses the glenohumeral joint laterally and
attaches to the acromion process of the scapula proximally.
The posterior deltoid crosses the glenohumeral joint posteriorly and attaches to the spine of the scapula proximally.
3. The proximal attachments of the deltoid are the same as the
lateral attachments of the trapezius, namely, the lateral clavicle, the acromion process, and the spine of the scapula.
4. Note how the deltoid fans around the glenohumeral joint.
It crosses the glenohumeral joint anteriorly, laterally, and
posteriorly. This orientation is similar to the orientation of
the gluteus medius to the hip joint. Therefore both of these
muscles can do the same actions at their respective joints.
The deltoid abducts, flexes, extends, medially rotates, and
laterally rotates the arm at the glenohumeral joint. The
gluteus medius abducts, flexes, extends, medially rotates, and
laterally rotates the thigh at the hip joint.
5. The anterior and posterior fibers of the deltoid are longitudinal (nonpennate). The middle fibers are multipennate.
6. Because it is pennate, the middle deltoid functions more for
stabilization (in the frontal plane). The anterior and posterior fibers, being longitudinal (nonpennate), function more
for movement (in the sagittal plane).
5
Ulna
Extensor
carpi
ulnaris
Extensor
digiti
minimi
Flexor
carpi
radialis
Extensor
digitorum
Palmaris
longus
Pronator
teres
Medial
epicondyle
Bicipital
aponeurosis
Brachialis
Triceps
brachii
Biceps
brachii
Brachial
artery
Figure 6-4
Ulnar
nerve
Median
nerve
Pectoralis
major
Coracobrachialis
Deltoid
Clavicle
Upper
trapezius
6
Flexor
digitorum
superficialis
Flexor
carpi
ulnaris
Medial View of the Muscles of the Right Elbow Joint
148
PART 2 The Skeletal Muscles of the Upper Extremity