the shoulder is a complex joint that is often mistreated, misdiagnosed and not understood. it is made up of 4 joints, and all of them play an important role in proper shoulder function. the clavicle makes up half of two of these joints, the acromioclavicular joint (where your collar bone attaches to your shoulder blade) and the sternoclavicular joint (where your collar bone attaches to your sternum). 7 different muscles (or parts of muscles) and 2 ligaments also attach on the clavicle. yet, most people don’t examine clavicular position and motion when looking at shoulder pain and performance. it undoubtedly can play a large role in function of the shoulder.
the typical resting angle of a clavicle is anywhere from 6 to 20 degrees of upslope. as mentioned above, a variety of restrictions will play a role in where you start and inevitably effect how you finish. restrictions from muscles that act on the clavicle can ultimately effect shoulder elevation, abduction, extension, and internal and external rotation as well as have an influence on the ability of the scapula to properly tilt. these motions are going to have to work together to assure proper shoulder movement into full range of motions without compensations from other places such as the thoracic and lumbar spine.
A depressed or flat collar bone can be caused by muscle restrictions from subclavius, latissimus dorsi, the internal rotators of rotator cuff, pec tightness, breathing pattern impairments, and other limiting factors. For the purpose of this blog, we are going to focus solely on the subclavius muscle. This muscle is the epitome of the quote “little hinges swing big doors.”
The subclavius is a small muscle that draws the clavicle inferior and anterior (down and forward). Restrictions in this muscle will limit full clavicular elevation, retraction and posterior rotation. To put that into reference of how much it could limit shoulder motion, the clavicle is required to elevate 11-15 degrees, posteriorly rotate 15-31 degrees, and retract 15-29 degrees during shoulder elevation. As you can imagine, being completely limited in these motions could cause a great deal of dysfunction and pain not only with shoulder elevation but also with the other motions that we discussed.
Because of the articulation between the clavicle and scapula and the acromioclavicular joint, a restriction in this small muscle may be a reason for decreased posterior tilting of the scapula. Posterior tilting of the scapula is necessary for overhead throwing, and full overhead motion of the arm. While much attention, and rightfully so, is paid to the pec major and minor, little to no attention is paid to the subclavius. Decreased posterior tilting of the scapula can also result in increased anterior tilt, which can lead to "impingement" syndrome, rotator cuff irritation, scapular winging, and other shoulder dysfunctions.
Limited shoulder range of motion has a correlation with injuries in throwers over the course of a season. It can often first show itself in the form or shoulder or elbow pain. As you can see this small muscle plays a great role in shoulder range of motion. Often, health care providers will relentlessly attack the lats, teres, subscapularis, and pecs, because of their ATTACHMENT directly to the arm, without looking at the axial structures that will indirectly affect shoulder function. but That isn’t the only way this little muscle can cause pain.
Look at the referred pain pattern by this muscle:
It is essentially the whole arm. Because of the close proximity to many important neurological and vascular structures the subclavius muscle has an extremely large muscle REFERRal pain pattern. Which brings us to our next point...
THE SUBCLAVIUS ALSO CAN DEPRESS THE CLAVICLE ENOUGH TO INTRUDE ON OTHER STRUCTURES.
if the restrictions from the subclavius are great enough it can depress the clavicle enough intrude on arteries (subclavian, suprascapular, axillary, ect.) and nerves (pectoral nerves, cutaneous nerves of the arm and forearm, subscapular, thoracodorsal, ect..) that deliver blood and innervation to the muscles of the arm. The subclavius role in the depression of the clavicle can be the cause of that numbeness, tingling, pain and decrease function of the entire arm.
But it’s so small how can you tell?
The first step to evaluating the subclavius muscle as part of the problem is to observe resting clavicular angle and perform a thorough palpation of the muscle. If there is a restriction or dysfunction of the subclavius muscle you will see a flat clavicle and it will typically be tender to palpation. Pressing on this muscle might lead to pain or sensation into any of the areas that are in red above. It is important to watch the clavicle motion in both active and passive range of all shoulder and scapula motions.
What should I do about it?
Well first off you should see a qualified physical therapist or other health care professional to get properly evaluated. If the subclavius is the true culprit for stealing your range of motion in your shoulder and causing your shoulder pain there are some interventions as well as corrective exercises you can perform. In general, soft tissue work directly to the muscle, joint mobilizations of the AC and SC joints, and scapular upward rotation exercises can be helpful. The neck in general is a great place to perform manual therapy and achieve a decrease in pain and increase in function.