The Shoulder = glenohumeral jt
• The glenohumeral joint is a
ball-and-socket joint that
allows for the arm to move in
a circular rotation as well as
movement of the arm
towards and away from the
body. The motion that the
glenohumeral joint provides
is flexion, extension,
abduction and adduction.
In Anatomical Position, the head of the
humerus is medial, slightly posterior
and superior in the glenoid fossa.
While the glenoid cavity faces laterally
forward and superior.
Acromioclavicular Joint (AC joint)
• a gliding joint within the shoulder. This joint
is specific to primates and humans,
allowing for the ability to raise the arm
above the head. This joint functions as a
pivot point, acting like a strut to help with
movement of the scapula resulting in a
greater degree of arm rotation. Also, the
AV joint allows for the transmission of
force from the upper arm to the rest of the
skeleton
The AV joint is formed
between the clavicle and the
scapula. The acromion, a
section of the scapula, is the
binding site for the clavicle.
These two bones fit together,
but are not stable on their
own. Ligaments & muscles
are used to stabilize the AV
joint.
Two sets of muscles are important for the stabilization of this joint in the
proper joint formation. [ help stabilize the clavicle and the scapula]
1) the trapezius: The upper trapezius muscle fibers connects the lower
base of the skull to the clavicle. The middle and lower trapezius muscle
fibers connect vertebrae in the spine to the scapula.
2) the deltoid: The anterior deltoid connects the clavicle to the humerus,
while the posterior and lateral deltoid fibers connect the scapula to the
humerus.
Trapezius
• Large superficial, flat triangular muscle of upper back. Originates on
the occipital bone of skull, ligamentum nuchae and 7 cervical and all
thoracic vertebrae and inserts onto the clavicle, acromion and spine
of the scapula.
• Because the fibers run in different directions, it has a variety of
actions. Different fibers control different actions:
• The superior (upper) fibers elevate the scapula: scapular elevation
(shrugging up),
• the middle fibers retract it: scapular adduction (drawing the shoulder
blades together)
• The inferior (lower) fibers depress it: depression (pulling the
shoulder blades down)
• When the superior and inferior fibers act together
they superiorly (upwardly) rotate the scapula.
Deltoids
• forms the rounded contour of the human
shoulder.
Origin
• It arises in three distinct sets of fibers
• Anterior fibers: from the anterior border and
upper surface of the lateral third of the clavicle
• Middle fibers: from the lateral margin and upper
surface of the acromion.
• Posterior fibers: from the lower lip of the
posterior border of the spine of the scapula, as
far back as the triangular surface at its medial
end
Insertion
• All the fibers converge, the middle passing
vertically, the anterior obliquely backward
and lateralward, the posterior obliquely
forward and lateralward;
• they unite in a thick tendon, which is
inserted into the V-shaped deltoid tubercle
on the middle of the lateral aspect of the
shaft of the humerus.
Action
• The anterior fibers: shoulder abduction when
the shoulder is externally rotated.
• The posterior fibers: involved in transverse
extension. The posterior deltoid is also the
primary shoulder hyperextensor.
• The lateral fibers: shoulder abduction when
the shoulder is internally rotated, are involved in
shoulder flexion when the shoulder is internally
rotated, and are involved in shoulder transverse
abduction (shoulder externally rotated) -- but are
not utilized significantly during strict transverse
extension (shoulder internally rotated).
Rotator Cuff
an anatomical term given to the
group of muscles & their tendons
that act to stabilize the shoulder.
Function of Rotator Cuff
hold the head of the humerus in the small
and shallow glenoid fossa of the scapula.
During elevation of the arm, the rotator
cuff compresses the glenohumeral joint in
order to allow the large deltoid muscle to
further elevate the arm. In other words,
without the rotator cuff, the humeral head
would ride up partially out of the glenoid
fossa and the efficiency of the deltoid
muscle would be much less.
Muscles comprising rotator cuff
•
•
•
•
Supraspinatus
Infraspinatus
Teres Minor
Subscapularis
• A mnemonic to remember what muscles
form the rotator cuff is SITS
(supraspinatus, infraspinatus, teres minor,
subscapularis)
Rotator Cuff Injury
• injury to 1 or more of the 4 muscles in the
shoulder. This shoulder injury may come on
suddenly and be associated with a specific injury
such as a fall (acute), or it may be something
that gets progressively worse over time with
activity that aggravates the muscle(s) (chronic).
• can range from an inflammation of the muscle
without any permanent damage, such as
tendinitis, to a complete or partial tear of the
muscle that might require surgery to fix it.
Chronic tear
• Found among people in occupations or
sports requiring excessive overhead
activity (examples: painters, baseball
pitchers)
• Variations in the shoulder structure
causing narrowing under the outer edge of
the collarbone
Symptoms
– Occur more often in a person's dominant arm
– More commonly found among men older than 40 years
– Pain usually worse at night and interferes with sleep
– Worsening pain followed by gradual weakness
– Decrease in ability to move the arm, especially out to the side
– Able to use arm for most activities but unable to use the injured arm for
activities that entail lifting the arm as high or higher than the shoulder to
the front or side
Acute tear
• Sudden powerful raising of the arm against
resistance, often in an attempt to cushion a fall
(examples: heavy lifting, a fall on the shoulder)
• Injury usually associated with a significant
amount of force if person is younger than 30
years
Symptoms
• Sudden tearing sensation followed by severe pain shooting through
the arm
• Motion limited by pain and muscle spasm
• Acute pain from bleeding and muscle spasm (often goes away in a
few days)
• Point tenderness over the site of rupture
• With large tears, inability to raise the arm out to the side, although
this can be done with help
Tendinitis
• Degeneration (wearing out) of the muscles
with age
• Repetitive trauma to the muscle by
everyday movement of the shoulder
Symptoms
– More common in women aged 35-50 years
– Deep ache in the shoulder also felt on the outside upper arm
– Point tenderness
– Pain comes on gradually and becomes worse with lifting the arm
to the side or turning it inward
– May lead to a chronic tear
When to call the doctor
• If shoulder pain lasts more than 2 days
• If shoulder problems (pain) do not allow you to work
• If you are unable to reach overhead to get an item in a
cabinet above shoulder level, for example
• If you are unable to play a certain sport such as baseball
or engage in an activity such as swimming
When to go to the hospital
• For any acute injury in which you are
unable to move the injured shoulder as
well as the uninjured shoulder, seek
emergency medical care.