Why is evaluation of the sternoclavicular joint important?
The sternoclavicular joint is where the clavicle (collar bone) meets the rib cage. It is an interesting joint because it is the central attachment of the shoulder to the trunk, but also because of its often-overlooked dynamic function and relationship to shoulder health. The sternoclavicular joint allows the clavicle, and therefore the shoulder, to move in many different directions. The motions of the clavicle include up, down, forward, back, rotations along its axis and can also be limited by a wide arrangement structures including bones, ligaments, muscles, and neurovascular structures. A joint that seemed so innocent is now much more complex and plays a much greater role in shoulder health than you may have expected.
During arm elevation, the clavicle can provide up to 30 degrees of elevation and 30-50 degrees of rotation. Of the 60 degrees of movement that comes from the scapula on the rib cage 40 degrees comes from the sternoclavicular joint. Any variance or decreased function of this joint can lead to poor movement quality and compensations down the chain in the AC joint, glenohumeral joint or scapulothoracic joint. This large amount of range of motion allows for proper shoulder function but is can easily be effected by the structures that attach to the bone. This brings us to our first point in evaluation of the SC joint.
Resting position can tell us a lot
When initially evaluating the SC joint you can get a lot of information from simply looking at the resting position of the clavicle. The typical resting position is anywhere from 6-20 degrees of upslope. Because the clavicle allows for such great range of motion, any decrease in resting position of the clavicle can cause the shoulder to be playing catch up from the onset of movement.
As you can see in the image above, many structures use the clavicle as an attachment site. Certain muscles such as the subclavius, pectoralis, and trapezius can become restricted and depress and downwardly rotate the clavicle. These restrictions can lead to decreased arm elevation in both forward and side motions as well as decreased internal and external rotation of the shoulder, as well as apply compression to all the structures that lie under the clavicle.
The Importance of addressing the depressed resting position
The depressed resting position is crucial to identify in any case of shoulder or arm pain. An extremely important neurovascular bundle lies directly under the clavicle. This bundle provides all vascular and nerve signals to the entire arm. A depressed clavicle may apply compression to this bundle and therefore decrease the structures ability to function properly. Without the proper conduction of nerve signals, and appropriate amount of blood flow the arm cannot functional optimally and will have symptomatic side effects. These symptoms may include decreased muscle tone and performance, numbness and tingling in the arm and hand, and decreased sensation or fine motor skills. All symptoms that could greatly influence performance, especially in a baseball player.
If the clavicle is depressed it also puts a baseball player at a greater risk of injury. Many UCL injuries occur at the point where a thrower reaches maximal external rotation. Depression of the clavicle can limit posterior rotation of the clavicle and therefore limit external rotation of the shoulder.
How to Address the Flat Clavicle
After a proper evaluation and assessment of the shoulder complex, and discovery that the sternoclavicular joint may be the issue there are several actions that may be taken. For starters, soft tissues work to the restrictive structures that may include massage, manual therapy, or self-soft tissue mobilization, next you want to try and promote clavicular elevation and rotation with exercises such as wall angles and wall slides. After promotion of proper movement, we can load the movement with exercises such as landmine press or a KB overhead press. It is important that you see a great rehab professional when dealing with shoulder pain. Even in a case like this, a flat clavicle may not be so cut and dry. There are secondary structures that can even lead to a case like this. For example, the pec minor pulling on the shoulder blade and secondarily causing a flat clavicle. Sternoclavicular movement must be assessed both statically and dynamically.
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