Shoulder impingement really is a pretty broad term that most of us likely take for granted. It has become much of a junk term, such as “patellofemoral pain.” The use of nondescriptive terminology, like “shoulder impingement,” is fine when describing the injury to the general public, but as professionals, it is in our best interest to be as descriptive as possible to assure to assess and treat the person appropriately.
There is no magical “shoulder impingement protocol” that you can pull out of your notebook and apply to a specific person.
There are three things that I consider to classify and differentiate shoulder impingement:
Shoulder Impingement: 3 Keys to Assessment and Treatment
1. Location – This is general in reference to the side of the rotator cuff that the impingement is located, either the bursal side or articular side. See the photo of a shoulder MRI below. The bursal side is the outside of the rotator cuff, shown with the red arrow. This is probably your “standard” subacromial impingement that everyone refers to when simply stating “shoulder impingement.” The green arrow shows the inside, or articular surface, of the rotator cuff. Impingement on this side is termed “internal impingement.” The two are different in terms of cause, evaluation, and treatment, so this first distinction is important. More about these later.
2. Impinging Structures – To me, this is more for the bursal sided, or subacromial, impingement and refers to what structure the rotator cuff is impinging against. As you can see in the pictures below (both side views), your subacromial space is pretty small without a lot if room for error. In fact, there really isn’t a “space”, there are many structures running in this area including your rotator cuff and subacromial bursa. You actually “impinge” every time you move your arm. Impingement itself is normal and happens in all of us, it is when it becomes excessive that pathology occurs. I try to differentiate between acromial and coracoacromial arch impingement, which can happen in combination or isolation. There are fairly similar in regard to assessment and treatment, but I would make a couple of mild modifications for coracoacromial impingement, which we will discuss below.
3. Cause of Impingement – This is what I refer to as “primary” and “secondary”shoulder impingement. Primary impingement means that the impingement is the main problem with the person. A good example of this is someone that has impingement due to their anatomy, with a hooked tip of the acromion like this in the picture below. Many acromions are flat or curved, but some have a hook or even a spur attached to the tip (drawn in red):
Secondary impingement means that someone is causing impingement, perhaps their activities, posture, tightness, or muscle imbalances are causing the humeral head to shift in it’s center of rotation and cause impingement. The most simply example of this is weakness of the rotator cuff. In this scenario, the deltoid will overpower the cuff and cause the humeral head to superiorly migrate, thus impinging the cuff between the humeral head and the acromion:
Differentiating Between the Types of Shoulder Impingement
In our DVD Optimal Shoulder Performance, we talk about different ways to assess shoulder impingement that may impact your rehab or training. There are specific tests to assess each type of impingement we discussed above. The two most popular tests for shoulder impingement are the Neer test and the Hawkins test. In the Neer test (below left), the examiner stabilizes the scapula while passively elevating the shoulder, in effect jamming the humeral head into the acromion. In the Hawkins test (below right) the examiner elevates the arm to 90 degrees of abduction and forces the shoulder into internal rotation, grinding the cuff under the subacromial arch.
You can alter these tests slightly to see if they elicit different symptoms that would be more indicative to the coracoacromial arch type of subacromial impingement. This would involve the cuff impingement more anteriorly so the tests below attempt to simulate this area of vulnerability. The Hawkins test (below left) can be modified and performed in a more horizontally adducted position. Another shoulder impingement test (below right) can be performed by asking the patient to grasp their opposite shoulder and to actively elevate the shoulder.
There is a good chance that many patients with subacromial impingement may be symptomatic with all of the above tests, but you may be able to detect the location of subacromial impingement (acromial versus coracoacromial arch) by watching for subtle changes in symptoms with the above four tests.
Internal impingement is a different beast. This type of impingement, which is most commonly seen in overhead athletes, is typically the result of some hyperlaxity in the anterior direction. As the athlete comes into full external rotation, such as the position of baseball pitch, tennis serve, etc., the humeral head slides anterior slightly causing the undersurface of the cuff to impingement on the inside against the posterior glenoid rim and labrum. This is what you hear of when baseball players have “partial thickness rotator cuff tears” the majority of time.
The test for this is simple and is exactly the same as an anterior apprehension test. The examiner externally rotates the arm at 90 degrees abduction and watches for pain. Unlike the shoulder instability patient, someone with internal impingement will not fell apprehension of anterior symptoms. Rather, they will have a very specific point of tenderness in the posterosuperior aspect of the shoulder (below left). WHen the examiner relocates the shoulder by giving a slight posterior glide of the humeral head, the posterosuperior pain diminishes (below right).
3 Keys to Treating Shoulder Impingement – How Does Treatment Vary?
There are three main keys from the above information that you can use to alter your treatment and training programs based on the type of impingement exhibited:
- Subacromial Impingement – Differentiate between acromial and coracoacromial impingement: Treatment is essentially the same between these two types of subacromial impingement, however, with coracoacromial arch impingement, you need to be cautious with horizontal adduction stretching. This is unfortunate as the posterior soft tissue typically needs to be stretched in these patients, but you can not work through a pinch with impingement! A pinch is impingement! Also, I would avoid elevation in the sagittal plane or horizontal adduction exercises.
- Primary versus secondary impingement – This is an important one and often a source of frustration in young therapists and trainers. If you are dealing with secondary impingement than you can treat the persons symptoms all you want, but they will come back if you do not address the route of the pathology! This is where a more global look at the patient, their posture, muscle imbalances, and movement dysfunction all come into play. Break through and see patients in this light and you will see much better outcomes.
- Internal impingement – One thing to realize with internal impingement is that it is pretty much a secondary issue. It is going to occur but any cuff weakness, fatigue, or loss of the ability to dynamically stabilize and the athlete will show some hyperlaxity in this athletic cocked shoulder position. Treat the cuff and it’s ability to dynamically stabilize to relieve the impingement.
Learn Exactly How I Evaluate and Treat the Shoulder
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