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The pectoralis minor is the smaller sister of the larger and more talked about pectoralis (pec) major. But for such a small, seemingly insignificant muscle, it can sure cause some problems!

The pec minor lives underneath its larger sibling, originating from ribs 3, 4 and 5 and passing superiorly and laterally to attach to the coracoid process of the scapula. Its jobs are to stabilize the scapula, as well as depressing, protracting and downwardly rotating it. When the scapula is fixed, pec minor will also assist in elevating the ribcage.

The pec minor plays a significant role in posture, shoulder stability and balance. With posture, we are doomed with our anterior dominant positions, hunched shoulders and horrible posture. Habitually holding this position, in which the pec minor is shortened for extended periods, often results in a facilitated, overactive, tight, shortened (or whatever adjective you want to use) pec minor.

Probably the most common injury to occur as a direct result of a short pec minor is subacromial impingement. In this condition, a lack of space below the subacromial arch causes the underlying tendons (typically supraspinatus, and also the subacromial bursa) to be impinged or “pinched” or “smooshed” with arm movements above shoulder height and especially with a rotational element. If there is inflammation or connective tissue thickening, there is not enough space below the arch, kind-of like when you over pack and you sit on your suitcase to zip it, the shoulder is the same way when it is too full in that space.

Does this sound like you? What to do?? This lack of space below the subacromial arch can be directly linked to an overactive pec minor protracting (shoulders rounding forward), anteriorly tilting and downwardly rotating the scapula, effectively lowering the subacromial arch. So now, we need to spend more time retracting and balancing out the space.

This altered position requires the elevator scapulae (neck muscle) and upper fibers of trapezius to increase potentiation in an attempt to maintain glenohumeral stability. The end result in this scenario is the tight neck and shoulders with active trigger points, as suffered by so many athletes and desk workers from these muscles working overtime.

Left alone and untreated, you are paving the way to  thoracic outlet syndrome (TOS) :-(. The good ole’ pec minor is also responsible for up to 50 percent of cases of TOS, aka pec minor syndrome. TOS is due to a compression of the nerves and blood vessels found in the chest and anterior shoulder (the brachial plexus and subclavian artery and vein).

Clearly, the pec minor can cause significant problems for the shoulder joint, neck and upper limb in particular. Ultimately, the pec minor can have a significant effect on the lower back and pelvis as a result of compensations occurring throughout the kinetic chain, but we’ll save that for another blog.

Pec Minor Assessment

To do a little bit of self assessment, look at the following:

  1. Posture – if the pec minor (pm) is tight, you will see the scapula winging, or sticking out.
  2. Thumbs – If your thumb is facing your thigh, your pm is tight! Your arm should not be internally rotated, thumb should be facing forward.
  3. Lie on your back and have someone measure the hight of the posterior acromion process (side bone on your shoulder) off the floor. 1″ or more, and that sucker is too tight! Compare measurement from left to right.
  4. Look at the above picture and find the 3 parts to your pm and palpate to see if tight and tender.


Pec Minor Treatment

This little bugger is a tough one to stretch, however, it responds immediately to manual massage therapies. In our next blog we will address some more therapy and stretching for the pm.