Rotator cuff

#t2

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(View in the front) Pasted image 20240605090810.png (like you put your hand on someone's shoulder from the back) Pasted image 20240605091026.png Pasted image 20250202161343.png

Supraspinatus (suprascapular nerve)
- Abducts arm initially (before the action of the deltoid)
- Most common rotator cuff injury (trauma or degeneration and impingement leading to tendinopathy or tear)
- Assessed by the "empty/full can" test
Infraspinatus (suprascapular nerve)
- Externally rotates arm
- The only one of these four muscles that does not participate in abduction.
- Common pitching injury
Teres minor (axillary nerve)
- Adducts and externally rotates arm
Subscapularis (upper and lower subscapular nerves)
- Internally rotates and adducts arm

Abduction of the upper limb

(0°-15°) Abduction of the upper extremity is initiated by the supraspinatus muscle (suprascapular nerve).
(15°-110°) Further abduction to the horizontal position is a function of the deltoid muscle (axillary nerve).
(110°-180°) Raising the extremity above the horizontal position requires scapular rotation by action of the trapezius (accessory nerve CN XI) and serratus anterior (long thoracic nerve).

Mnemonic

"Start Dancing, Then Spin!"

Start (Supraspinatus: 0°–15°)
Dancing (Deltoid: 15°–110°)
Then (Trapezius: 110°–180°)
Spin! (Serratus anterior: 110°–180°)