The Rotator Cuff Muscles

Infraspinatus

FUNCTION: External Rotation ORIGIN: Infraspinatus Fossa INSERTION: Greater Tuberosity NERVE INNERVATION: Suprascapular Nerve EXTRA INFO: Most active when = arm is in neutral performing external rotation (ER) . Attributes 90% of power (strength, force) during external rotation (ER)

Teres Minor

FUNCTION: External Rotation ORIGIN: lateral (axillary) border of the scapula INSERTION: Greater Tuberosity NERVE INNERVATION: Axillary Nerve EXTRA INFO: Most active when = in EXTERNAL rotation (ER) with shoulder abducted to 90 degrees.

Subscapularis

FUNCTION: Internal Rotation ORIGIN: Subscapular Fossa INSERTION: Lesser Tuberosity NERVE INNERVATION: Subscapular Nerve EXTRA INFO: Provides 50% of rotator cuff strength Main internal Rotator

Supraspinatus

FUNCTION: Shoulder Abduction (w/the middle deltoid) ORIGIN: Supraspinatus Fossa INSERTION: Greater Tuberosity NERVE INNERVATION: Suprascapular Nerve EXTRA INFO: Most common rotator cuff injury due to location directly underneath the acromion (tight space) Critical Zone Area (where and why): where the supraspinatus inserts into the Greater tuberosity (where) because it is an area with poor blood supply (why)

Rotator Cuff Info

FUNCTION: be a force couple to control the head of the humerus on the glenoid fossa 5th Rotator Cuff muscle: Long head of the bicep brachii Function of the 5th rotator cuff muscle: prevents superior migration of the humeral head *during shoulder ELEVATION the RTC compresses and inferiorly glides the humeral head.

Kinesiology of the Shoulder Complex (during shoulder elevation)

STERNOCLAVICULAR JOINT: posterior axial rotation of clavicle (31 degrees), retraction, and elevation ACROMIOCLAVICULAR JOINT: posterior tilting of the scapula (19 degrees) GLENOHUMERAL JOINT: elevation and external rotation (ER) SCAPULOTHORACIC JOINT: abduction and upward rotation