The Infraspinatus and Teres Minor Muscles

 

Remember that there are four rotator cuff muscles and this month we’re doing numbers two and three. I have put these two muscles together for this month’s ‘muscle of the month’ series based on their action (external rotation). The first rotator cuff muscle was the supraspinatus muscle last month. Next month we’ll wrap it up with the subscapularis.

What does infraspinatus mean?

Its name describes its location (below the spine). Infra means below or underneath and spina refers to a spine in this case referring to the spine or ridge of the scapula.

What does teres minor mean?

Teres means rounded and minor refers to the fact that it is the smaller of the two “teres” muscles.  (Teres major is not one of the muscles of the rotator cuff).

Where do infraspinatus and teres minor attach?

Origin

• Infraspinatus originates on the infraspinous fossa on the scapula and covers the lower two-thirds of the scapula.
• Teres minor originates on the middle portion of the lateral edge of the scapula.

Insertion

• Both infraspinatus and teres minor attach on the head of the humerus.
• Infraspinatus may be partially or totally fused with teres minor in some people.

What actions do infraspinatus and teres minor do?

• Both infraspinatus and teres minor are external rotators of the humerus at the shoulder joint.
• All rotator cuff muscles help to stabilize the head of the humerus.

What are the most common injuries to infraspinatus and teres minor?

Infraspinatus is the second most likely of the rotator cuff muscles to get injured after the supraspinatus. A tear of the infraspinatus could be the result of either an acute or chronic movement.

Baseball pitcher’s classically tear the infraspinatus muscle. It’s not the acceleration of throwing the ball as much as it is the eccentric control of this muscle while they are throwing the ball that causes it to tear.

Trigger Points

By far, the most common issues I see in yogis are the development of trigger points in this muscle. This is especially true of practitioners that are regularly doing chaturanga, up-dog, and down dog. The shoulder has to stabilize through these movements and that is the job of the rotator cuff muscles in general.

Look at the trigger point patterns and you will see that the referral pattern is similar to what many people complain about in yoga.

Trigger points from the infraspinatus can radiate to the FRONT of the shoulder and down the arm!

Postures Where The Infraspinatus and Teres Minor are Lengthened

In Marichyasana C, the infraspinatus and teres minor are being lengthened due to the internal rotation of the right shoulder.

Postures Where The Infraspinatus and Teres Minor Contract

Trying to get the arms into eagle (external rotation of the shoulder) will cause both of these muscles to contract.