Kinesiology

Lesson 8 of 16

Shoulder and rotator cuff

The shoulder complex combines mobility with active stabilization. The rotator cuff muscles help center the humeral head and contribute to rotation or abduction, while scapular muscles coordinate the base. A painful shoulder may have many causes, so massage therapists should avoid diagnosing and work within the client's comfortable range. Position the arm with support rather than traction.

Key points

• The cuff comprises supraspinatus, infraspinatus, teres minor, and subscapularis.
• Supraspinatus assists early abduction and contributes to humeral-head stabilization.
• Infraspinatus and teres minor externally rotate the arm; subscapularis internally rotates it.
• Deltoid produces major shoulder abduction after the initial phase, with coordinated cuff activity.
• Scapular upward rotation supports full arm elevation.
• Stop or modify if movement produces sharp pain, guarding, or unusual symptoms.

Key terms

Supraspinatus

O: supraspinous fossa; I: superior facet of greater tubercle; A: initiates abduction and stabilizes shoulder.

Infraspinatus

O: infraspinous fossa; I: middle facet of greater tubercle; A: laterally rotates arm and stabilizes shoulder.

Teres minor

O: lateral border of scapula; I: inferior facet of greater tubercle; A: laterally rotates and weakly adducts arm.

Subscapularis

O: subscapular fossa; I: lesser tubercle of humerus; A: medially rotates and adducts arm.

Deltoid

O: lateral clavicle, acromion, and scapular spine; I: deltoid tuberosity; A: abducts arm; anterior fibers flex/medially rotate, posterior fibers extend/laterally rotate.