Infraspinatus pain referral zone:                

Infraspinatus is one of the four muscles of the rotator cuff. It originates on the dorsal surface of the scapula, and on the spine of the scapula, and inserts on the posterior aspect of the greater tuberosity of the humerus. Its principal function is to rotate the arm externally. Trigger points in infraspinatus refer to the back of the neck, the upper back between the scapula and the spine, and down the radial edge of the arm from the shoulder to the first two fingers.

Translation: "Infra" means "below." This muscle is below the spine of the scapula, which is a bony ridge running across the back of the shoulderblade near the top. It covers most of the back of the shoulderblade below this ridge, and attaches to the back of the top of the bone in your upper arm. Its job is to rotate your arm outward. Trigger points in this muscle can cause pain in the back of your neck, your upper back, and down the inner edge of your arm and wrist to your first two fingers.

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