Shoulder Girdle

Question 1

How much larger is the humeral head compared to the glenoid fossa?
What is a picture of the humeral head in the glenoid fossa.

Answer 1

The humeral head is 1/2 of a sphere. It is 2X the size of the glenoid fossa.
It is like balancing a golf ball on a tee that is being held sideways.

Question 2

How stable is the GH joint without muscles and ligaments? What are characteristics that affect the stability?

Answer 2

The humeral head and the glenoid fossa are very congruent. They meet perfectly in the same plane and orientation. However, the glenoid fossa is too small and shallow to provide complete stability for the humeral head. It is a congruent joint, but very unstable without muscles and ligaments.

Question 3

How is the humeral head oriented?

Answer 3

Directed medially, superiorly, and posteriorly.

Question 4

What are characteristics of the glenoid fossa?

Answer 4

The glenoid fossa is the size of a quarter.
It is oriented superiorly and 30-45 degrees anteriorly.
It has a labrum to provide stability to the joint.

Question 5

What is the labrum and what is its function?

Answer 5

1) The labrum is a ring of fibrocartilage around the rim of the glenoid fossa that deepens the fossa and provides stability to the joint.
2) It also acts as a “bumper” that keeps the head of the humerus in the joint
3) Increases surface area of the articulation which decreases pressure.
4) Reduces friction
5) Protects the bony rim of the fossa
6) Restricts excessive movements, but does not restrict full ROM

Question 6

What are some characteristics of fibrocartilage?

Answer 6

Fibrocartilage is the cartilage that is in disks, menisci, and the labrum. It is flexible and decent at absorbing compression forces. However, it does not absorb torsion well.

Question 7

How is the labrum typically torn? What decreases when you tear the labrum?

Answer 7

The labrum is typically torn with torsion - compression with a twist.
The labrum keeps the humeral head inside the fossa, so when you tear it, the humerus gets more unstable. It decreases stability.

Question 8

Is the GH joint capsule loose or tight? Why?

Answer 8

GH joint capsule is large and loose in general. If there is a lot of movement at a joint, you want a loose joint capsule. The capsule is reinforced by ligaments and tendons of muscles that blend into it.
If someone has a tight joint capsule that is restricting motion, that is what we try to stretch with joint mobilizations.

Question 9

What happens to the GH joint capsule when the UE is in a dependent position?

Answer 9

Capsule is tight superiorly, and slack anteriorly and inferiorly.

Question 10

Where does the Superior Glenohumeral Ligament insert on the humerus?
What makes it taut?

Answer 10

Inserts onto the anatomical neck above the lesser tubercle.

The SGHL gets tight when humerus glides downward or anteriorly. External rotation.

Question 11

Where does the Middle Glenohumeral Ligament insert on the humerus? What motion makes it tight?

Answer 11

Along the anterior aspect of the anatomic neck, also blends with the subscapularis tendon.
It restricts an anterior glide of the humerus, especially in about 45-90 degrees of abduction. External rotation causes an anterior translation of the humeral head, so it is limited by the MGHL.

Question 12

How many portions does the Inferior Glenohumeral Ligament have? What are they?

Answer 12

It has 3 portions: anterior, posterior, and axillary pouch.

Question 13

Where does the IGHL insert on the humerus?

What motion makes it taut?

Answer 13

As a broad sheet to the anterior-inferior and posterior-inferior margins of the anatomic neck.
Axillary pouch: 90 degrees of abduction, combined with anterior-posterior and inferior translations
Anterior band: 90 degrees of abduction and full external rotation; anterior translation of humeral head
Posterior band: 90 degrees of abduction and full internal rotation

Question 14

How does the IGHL work with shoulder movement?

Answer 14

IGHL is like a hammock that cups the inferior portion of the humeral head. When your arm is hanging, this ligament is curled up on itself. It doesn’t unfurl until you start to abduct your arm. Then it unfurls and cups the humeral head. This gives the humeral head stability and keeps it from gliding too far down as the humerus moves up in abduction.

Question 15

What are some pathologies that involve IGHL?

Answer 15

Frozen shoulder involves this ligament. Adhesive capsulitis also means this pouch won’t open all the way. If the pouch doesn’t open all the way, the humeral head can’t move down all the way, and the humerus can’t go all the way. This is why they can’t raise their shoulder all the way.

Question 16

What ligament blends in with the supraspinatus tendon? What is its function?

Answer 16

The coracohumeral ligament blends into the supraspinatus tendon and the superior capsule underneath the coracoacromial arch.
Creates a sling that keeps the biceps tendon in the intertubercular groove.
It also tightens with inferior translation of the humeral head which occurs during external rotation.

Question 17

Which ligament spreads across the bicipital groove?

Answer 17

The transverse humeral ligament spans the bicipital groove and holds the long head of the biceps tendon in the groove, so it doesn’t bow out.

Question 18

How is motion of the GH joint affected by where the muscle crosses it?

Answer 18

If the muscle crosses the front of the joint, it will flex the joint.
If it crosses the back, it will extend the joint.
If it crosses the side, it will abduct the joint.

Question 19

Why is static stability important for clients? What does static stability do?

Answer 19

Static stability keeps the humerus head in the joint. Without static stability, gravity would constantly pull the shoulder out of socket.
It keeps the humeral head centered on the glenoid fossa.

Question 20

Why is dynamic stability at the GH joint important?

Answer 20

Impingement is a major problem. Dynamic stability helps with full range of motion that is pain free.

Question 21

Explain adduction moment and the angle of the head of the humerus on the glenoid fossa.

Answer 21

Adduction moment is the promotion of a slight adduction of the humerus relative to the glenoid fossa. The glenoid fossa is oriented slightly superiorly. The adduction moment causes the angle between the head of the humerus and the glenoid fossa to be slightly acute instead of 90 degrees. This allows the gives the humeral head a lip to rest on that is created by the rim of the glenoid fossa and the labrum. These act as a buffer to prevent the humeral head from sliding down.

Question 22

What is static locking of the shoulder?

Answer 22

Gravitational force coupled with forces provided by superior structures locks the humeral head into the glenoid fossa. Gravity pulls the humeral head down into the buffer created by the rim of the glenoid fossa and the labrum and locks it in. The superior structures have tension in them to hold the humeral head into the glenoid fossa.

Question 23

Which superior structures participate in static locking?

Answer 23

• the superior capsule
• coracohumeral lig helps with positioning and maintaining stability
• supraspinatus gives static stability and restricts downward pull of humerus
• deltoid overlies whole joint and is always firing at low levels for stability. Mostly middle and posterior delt.
• long head of biceps tendon has fibers that join into the capsule, so it offers some passive restraint
• still unsure about stabilizing abilities of triceps. Probably not a primary stabilizer

Question 24

How does bad posture affect adduction moment and static locking?

Answer 24

When you have bad posture, the glenoid fossa loses its superior orientation.