How to Identify the Infraspinatus

The infraspinatus is a thick triangular muscle that fills the majority of the infraspinatous fossa. It is part of a group of muscles called the rotator cuff, along with the subscapularis, supraspinatus and teres minor. Athletes such as golfers, baseball pitchers and football quarterbacks frequently tear or impinge the rotator cuff. The following steps will help you identify the infraspinatus.

Instructions

Difficulty: Moderate

1. Read up on Latin roots to know that "infra" means "below" and "spinatus" means "spine." This muscle is "below the spine" of the scapula.
2. Examine the infraspinatus to see that it externally rotates and adducts the humerus. The infraspinatus also stabilizes the glenohumeral joint along with the other rotator cuff muscles.
3. Observe how the infraspinatus originates medially from the infraspinatous fossa and the infraspinatous fascia. It is attached by fleshy fibers on the medial two-thirds and tendinous fibers on the surfaced ridges.
4. Look at how the fibers of the infraspinatus converge to a tendon which passes over the lateral border of the scapula's spine and the posterior portion of the shoulder joint's capsule to insert into the middle facet of the humerus' greater tubercle. The tendon is occasionally separated from the shoulder joint's capsule by a bursa.
5. Research the nervous system to know that the nerve for the infraspinatus is the suprascapular nerve from the fifth and sixth cervical nerves. Study the circulatory system to know that the blood supply for the infraspinatus is the suprascapular artery and scapular circumflex artery.

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