1.4.4. Intrinsic Muscles of the Shoulder and Joint Stability / Motility Flashcards
What is the downside to the Glenohumeral Joint being the most Mobile in the Body?
It is at the Expense of Stability
What are the 3 factors which contribute to the Glenohumeral Joints mobility?
- The Type of Joint
- The Bony Surface Ratio
- The Laxity of the Joint Capsule
What type of joint is the Glenohumeral Joint?
A Ball and Socket Joint
What are the 2 articulating surfaces in the Glenohumeral Joint?
- Glenoid Cavity
2. Humerus
- Which if the 2 articulating surfaces of the Glenohumeral Joint is larger?
- By how much?
- The Head of the Humerus
2. By the ratio of 4:1 (Similar to a Gold Ball and a Tee)
What are the 3 factors which contribute to the Glenohumeral Joints stability?
- Rotator Cuff Muscles
- Glenoid Labrum
- Ligaments
What do Rotator Cuff Muscles attach to?
- The Tubercle of the Humerus
- The Scapula
- Fused with the Joint Capsule
What is the “Resting Tone” of the Rotator Cuff Muscles?
To pull the Head of the Humerus into the Glenoid Cavity
What are the 4 Rotator Cuff Muscles?
- Subscapularis
- Supraspinatus
- Infraspinatus
- Teres Minor
What movements, of the Glenohumeral Joint, are generated by Rotator Cuff Muscles?
- Abduction
- Lateral Rotation
- Medial Rotation
- Adduction
Where does the Subscapularis attach onto the Scapula?
The Subscapular Fossa (on the Costal (anterior) Surface of the Scapula)
Where does the Subscapularis attach onto the Humerus?
The Lesser Tubercle of the Humerus
What is the innervation of the Subscapularis?
The Upper and Lower Subscapular Nerves
What is the function of the Subscapularis?
To Medially Rotate the Arm
Where does the Supraspinatus attach onto the Scapula?
The Supraspinous Fossa
Where does the Supraspinatus attach onto the Humerus?
The Greater Tubercle of the Humerus
What is the innervation of the Supraspinatus?
The Suprascapular Nerve
What is the function of the Supraspinatus?
- Abducts the Arm 0-15 degrees
2. Assists the Deltoid Abduct the arm from 15-90 degrees