by Jay McCallum, PT, DPT, OCS
Board Certified Specialist in Orthopaedic Physical Therapy
What the heck is the serratus anterior?
Because the serratus anterior is largely hidden from view underneath the shoulder blade, it is remarkably easy for both patients and clinicians to forget about this vital muscle. It originates from the underside of the shoulder blade near the inner edge and has a broad attachment to the ribs. It gets its name from the way that it is serrated, like a knife blade, as it attaches into the ribs, and is anterior (forward to) the shoulder blade. Even though the serratus anterior is not visible on most people’s bodies, it is normally a very strong and fairly large muscle.
Serratus Anterior side view
Okay…so what does it do?
And here is where the confusion REALLY sets in. The serratus anterior has historically been though of as performing two primary functions. The first is to hold inner edge of the shoulder blade against the ribs, preventing ‘winging’ of the shoulder blade, as shown here.
Winging of the shoulder blade due to serratus weakness or paralysis
However, winging of this type is fairly rare, occurring mostly with injuries to the nerve that supplies the serratus anterior, the long thoracic nerve. The second commonly thought of function for the serratus anterior is ‘protraction’ of the shoulder blade, pushing it forward relative to the body in a punching motion.
So, the reader is thinking at this point, if my serratus anterior is weak then my right hook isn’t what it used to be, and I have a funny looking shoulder blade. Tell me again why this is important? Turns out that the serratus anterior does two other things that are a bit more functionally useful to us. The first is that it is the strongest, best positioned muscle to create upward rotation of the shoulder blade, basically aiming the socket up. In order to reach higher than about shoulder level the shoulder blade must upwardly rotate. If the serratus is weak, then the shoulder blade literally can’t get out of the way of the arm, and that leads to pinching at the top of the shoulder, frequently known as subacromial impingement syndrome or subacromial bursitis. Over time, it can even lead to development of a rotator cuff tear. The other really important function of the serratus is to solidly anchor the shoulder blade to the thorax with use of the arm. If the shoulder blade doesn’t have that stability, then the rotator cuff must work much harder, rather like walking in sand rather than on a hard surface makes your legs work harder. That can, in turn, lead to rotator cuff tendinitis.
What does this have to do with my neck pain?
The serratus anterior isn’t the only upward rotator of the shoulder blade, it’s just the best one. If it’s weak, the body goes looking for another way to accomplish the movement, and the next muscle in line is the upper trapezius.
The upper trapezius - look familiar?
Unfortunately, the upper trapezius is not particularly good at creating upward rotation of the shoulder blade, so in this role it has to work extremely hard, and so can become quite painful. It also attaches into the skull and upper neck, and so significantly compresses those structures when it is activated.
How would I know if my serratus is a problem?
Anybody with shoulder pain should certainly have their serratus anterior strength assessed by a physical therapist, as serratus anterior weakness and/or inhibition is extremely common to a range of painful shoulder conditions. The serratus anterior should also be examined for most patients with neck pain, particularly those who find that their pain is brought on by use of their arms – i.e. experiencing neck pain with lifting, carrying, cleaning, etc.
What can I do about it?
Like most muscles, serratus anterior strength is very activity-specific. A common pattern is that a patient may be able to generate significant force into protraction – the ‘punching’ motion, but have much less strength with upward rotation of the shoulder blade. And if there is a strong compensatory pattern already in place it can be quite difficult to re-establish a more efficient movement pattern. So, while the internet has many serratus anterior exercises a short Google search away, people with symptoms are best advised to seek the guidance of a physical therapist, who can identify the specific pattern of weakness that may be present and design an individualized exercise program to address it.
If you’re in Flagstaff or northern Arizona and want this type of evaluation, then please call us at 928-556-9935 or email us for an appointment!