Shoulder impingement is a really broad term that is used too often. It has become such a commonly used junk term, such as “patellofemoral pain,” especially with physicians.
Other common variations include subacromial impingement or rotator cuff impingement, but it seems as if any pain originated from around the shoulder is often labeled as “shoulder impingement.”
Unfortunately, the use of such a broad term as a diagnosis is not helpful to determine the treatment process. There is no magical “shoulder impingement protocol” that you can pull out of your pocket and apply to a specific person.
I wish it were that simple.
This is also why conclusions are difficult to be drawn from meta-analysis and systematic reviews. A paper looking at hundreds of people age 25-65+ with “shoulder pain” isn’t going to provide much clarity, it’s too diluted.
Luckily, a thorough examination can be used to determine the best treatment plan. Each person will likely present differently, which will require variations on how you approach their shoulder rehabilitation.
Most of the clinical examination for shoulder impingement involves provocative tests. Those are great, but the real challenge when working with someone with shoulder impingement isn’t figuring out that they have shoulder pain, that’s fairly obvious. That’s why they are there.
It’s figuring out WHY they have shoulder pain, and what to do about it.
Shoulder Impingement: 3 Keys to Assessment and Treatment
To make the treatment process for shoulder impingement a little more simple, there are 3 things that I typically consider to classify and differentiate shoulder impingement.
- The location of shoulder impingement
- The structures involved
- The underlying cause of shoulder impingement
Each of these can significantly vary the treatment approach and how successful you are treating each person.
If you approach each patient with these 3 things in mind, you are going to do a much better job developing an effective treatment plan, versus just trying things and hoping they work.
I’ve called this the corrective exercise bell curve in the past. If you just throw the same treatments at every person with shoulder pain, you’ll probably get lucky 20% of the time, make them worse 20% of the time, and simply waste your time the rest.
Let’s dig in…
Location of Shoulder Impingement
The first thing to consider when evaluating someone with shoulder impingement is the location of impingement. This is generally in reference to the side of the rotator cuff that the impingement is located, either the outside of the rotator cuff or the undersurface of the rotator cuff.
These are broken down into either:
- Bursal sided shoulder impingement – this is your traditional subacromial impingement
- Articular sided shoulder impingement – this is called internal impingement
Bursal Sided Shoulder Impingement
See the photo of a shoulder MRI above (photo credit). The bursal side is the outside of the rotator cuff, shown with the red arrow. This is probably your “standard” subacromial impingement that most people refer to when simply stating “shoulder impingement.”
This is often called subacromial impingement because of the location of impingement occurs between the rotator cuff and the undersurface of the acromion, hence the term “subacromial.” This is also called the bursal side of the rotator cuff because there is a bursa located between the rotator cuff and the acromion, which acts as a shock absorber.
Articular Sided Shoulder Impingement
The green arrow shows the undersurface, or articular surface, of the rotator cuff. This Impingement on this side is often termed “internal impingement” because the impingement occurs on the inside, or joint side, of the rotator cuff. If you look closely in the image above, the yellow arrow shows an articular sided partial thickness rotator cuff tear. Note the irregularity of white at the bottom of the dark line of the rotator cuff.
This often involves the supraspinatus and infraspinatus rotator cuff muscles as the undersurface impinges against the glenoid joint rim. I’ll go over this in more detail below.
The two types of impingement are completely different and occur for different reasons, so this first distinction is important.
Because the cause of shoulder impingement is so different, the evaluation and treatment of subacromial and internal impingement will also be completely different. More about these later when we get into the evaluation and treatment.
Impinging Structures Involved
The next factor to discuss is which structures are involved in the shoulder impingement. This is more for the bursal sided, or subacromial impingement, and refers to what structure the rotator cuff is impinging against.
Take a look at the shoulder from the side view, with the front of the shoulder to the right and the back of the shoulder to the left. You can see the acromion is superior and the coracoid is a little more anterior. The coracoacromial ligament runs between these two areas.
As you can see in the image, your subacromial space is pretty small (the red areas). It’s pretty easy to impinge on the acromion, coracoid, or coracoacromial arch. There isn’t a lot of room for error. In fact, this really isn’t a blank “space”, there are actually many structures running in this area including your rotator cuff and subacromial bursa.
Get ready… I’m about to blow your mind…
You actually “impinge” every time you move your arm. We all do.
That’s right, impingement of these structures itself is normal and happens in all of us every time we use our arms. It’s when this becomes abnormal, excessive, or too frequent that shoulder pain and pathology occurs.
This is why it is very shortsighted to say “impingement” is normal and that people should work through their discomfort. Yes, some impingement is normal, but excessive impingement is what may cause pain and pathology down the road.
So when it comes to the structures involved in impingement, I try to differentiate between subacromial and coracoacromial arch impingement. These can happen in combination or isolation and typically involve the supraspinatus rotator cuff muscle.
Another area that has received more attention lately is the subcoracoid space or the area below the coracoid. You can also have subcoracoid impingement. Because this is located more anteriorly, the subscapularis rotator cuff muscle can be involved with subcoracoid impingement.
The three types of bursal sided impingement are fairly similar in regard to assessment and treatment, but I would make a couple of mild modifications for coracoacromial and subcoracoid impingement, which we will discuss below.
So if we were to get very specific, you can break shoulder impingement down into four different types based on the location and structures involved:
Bursal sided impingement:
- Subacromial impingement – Involves the supraspinatus and acromion
- Coracoacromial impingement – Involves the supraspinatus and coracoacromial arch
- Subcoracoid impingement – Involves the subscapularis and coracoid
- Internal impingement – Involves the supraspinatus and infraspinatus and glenoid rim
See what I mean? How can all of these be “shoulder impingement?” They all involved different muscles, different impinging structures, different locations, and different mechanisms!
OK, great, we now have differentiated and know “what” is impinging, we still don’t know “why” the person has impingement.
Cause of Shoulder Impingement
The next thing to look at is the actual reason why the person is experiencing shoulder impingement.
There are two main classifications of causes that I refer to as “primary” or “secondary” shoulder impingement.
Primary 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 anatomical considerations, 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):
This also happens with the coracoid and subcoracoid impingement. An anatomical variation of the coracoid or bone spur can be present.
As our knowledge of shoulder impingement improves, it appears that the larger a bone spur, the more problematic it may become.
This is referred to as primary impingement because improving things like mobility, strength, and dynamic stability may be ineffective as there is a primary cause of impingement causing the symptoms.
Sure we may improve the symptoms and often times are successful with rehabilitation, but sometimes we aren’t. It’s not because a certain treatment “isn’t effective for shoulder impingement.” It’s because there is a primary reason why impingement is occurring that we can’t change.
Without addressing the primary issue, like a large bone spur, working on secondary issues may not be effective.
Secondary Shoulder Impingement
Secondary impingement means that something else is causing impingement, perhaps their activities, posture, lack of dynamic stability, or muscle imbalances are causing the humeral head to shift in its center of rotation and cause impingement.
The most simple example of this is weakness of the rotator cuff.
The rotator cuff and larger muscle groups, like the deltoid, work together to move your arm in space.
The rotator cuff works to steer the ship by keeping the humeral head centered within the glenoid. The deltoid and larger muscles power the ship and move the arm.
Both muscles groups need to work together.
If rotator cuff weakness is present, the cuff may lose its ability to keep the humeral head centered. In this scenario, the deltoid will overpower the cuff and cause the humeral head to migrate superiorly, thus impinging the cuff between the humeral head and the acromion:
This is just a simple example, but as you can see is very impactful for shoulder function. It’s not just weakness of the rotator cuff, it’s also imbalanced strength ratios and improper timing of dynamic stabilization.
Other common reasons for secondary impingement include mobility restrictions and poor dynamic stability of the shoulder, scapula, and even thoracic spine.
All of these areas need to work together to produce optimal shoulder function.
I see this a lot in my patients.
In the person below, you can see that they do not have full overhead mobility, yet they are trying to overhead press and other activities in the gym, flaring up their shoulder.
If all we did with this person was treat the location of the pain in his anterior shoulder, our success will be limited. He’ll return to the gym and start the process all over if we don’t restore this mobility restriction.
The funny thing about this is that people are rarely aware that they even have this limitation until you show them.
Also, keep in mind that this is not “chronic pain.” Sure this person has had shoulder pain for 8 months, but it’s because they keep irritating the area. This is more like recurring acute pain.
Differentiating Between the Types of Shoulder Impingement
In my online shoulder program on the Evidence Based Evaluation and Treatment of the Shoulder, I 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 special tests for shoulder impingement are the Neer test and the Hawkins test.
In the Neer test, the examiner stabilizes the scapula while passively elevating the shoulder, in effect impinging the humeral head into the acromion.
In the Hawkins test, the examiner elevates the arm to 90 degrees of abduction and forces the shoulder into internal rotation, impinging the cuff under the subacromial arch.
As I mentioned earlier, these special tests for shoulder impingement are provocative in nature, meaning that we are looking for reproduction of pain.
Both of them will cause the structures to impinge in all of us, but they shouldn’t produce pain. But if the area is sensitive and irritable, they will cause pain.
You can alter these tests slightly to see if they elicit different symptoms that would be more indicative to the coracoacromial arch or subcoracoid types of subacromial impingement.
Because these structures are more anterior, we can alter the tests to better assess this area.
The Neer test can be performed in the sagittal plane, and the Hawkins test can be modified and performed in a more horizontally adducted position. Both of these positions will impinge more anteriorly.
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.
Now, before we go any further, let’s talk briefly about the reported accuracy of these tests in the literature.
Just like we’ve talked about with the studies looking at the treatment effectiveness in people with shoulder impingement, most studies published vaguely look at how accurate a test may be at detecting “impingement.” Hopefully, if you’ve gotten this far in the article, you see how flawed this approach is, as this is simply too broad.
How can we evaluate how “specific” a special test is for such a “non-specific” diagnosis?
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 of the shoulder in the anterior direction.
As the athlete comes into full external rotation, such as the position of a baseball pitch, tennis serve, volleyball serve, and others, the humeral head slides anterior slightly causing the undersurface of the cuff to impingement on the inside against the posterior-superior glenoid rim and labrum.
This is what you hear of when baseball players have “partial thickness rotator cuff tears” the majority of the time. They aren’t the same partial thickness tears your grandmother has.
The best special test for internal impingement 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 symptoms. Unlike the shoulder instability patient, someone with internal impingement will not feel apprehension or 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?
Using the three main keys from the above information, you can alter your treatment and training programs based on the specific of impingement exhibited:
- The location of shoulder impingement – bursal or articular sided impingement
- The structures involved – Subacromial, coracoacromial arch, subcoracoid, or internal impingement
- The underlying cause of shoulder impingement – primary or secondary.
I promise you are going to have much more success in designing a physical therapy or training program if you factor in these keys.
Treating Different Types of Impingement
As I hope you can now see, to properly treat shoulder impingement you should differentiate between subacromial, coracoacromial, subcoracoid, and internal impingement.
Treatment is similar between these types of impingement. There is a bunch of overlap.
However, there are some differences:
- With subacromial impingement, you should be cautious with overhead activities that produce discomfort
- With the more anterior-based coracoacromial arch and subcoracoid impingement, you need to be cautious with elevation in more of a sagittal plane and horizontal adduction movements that produce discomfort
- With internal impingement, you should be cautious with excessive external rotation at 90 degrees abduction (like the throwing position) that produce discomfort
Notice that I said “that produce discomfort” for all three? The key here for me is that you should not work through discomfort or a “pinch” with impingement.
A “pinch” is impingement of a sensitive structure!
I’m not a fan of working through pain with shoulder impingement. That to me shows me that you either have a primary or secondary cause of impingement that hasn’t been addressed. Trying to work through this could actually just irritate it more.
Treating Primary Versus Secondary Shoulder Impingement
This is an important one and often a source of frustration in young clinicians.
If you are dealing with secondary impingement, you can treat the person’s symptoms all you want, but they will come back if you do not address the underlying reason why they have symptoms.
But please remember, I do treat their symptoms, that is why they have come to see me.
I want to reduce discomfort and inflammation. This is going to allow me to do more in the long term. However, this should not be the primary focus if you want long term success.
This is where a more global look at the patient, their posture, muscle imbalances, and movement patterns all come into play. Breakthrough and see patients in this light and you will see much better outcomes.
You should have a systemized way of assessing movement and building programs to optimize and enhance their function. If you don’t you really should check out my system in my free online Introduction to Performance Therapy and Training course.
A good discussion of the activities that are causing their symptoms may also shed some light on why they are having shoulder pain.
Again, using the example above, if you don’t have full mobility and try to force the shoulder through this motion restriction you are going to likely cause some irritation.
This is especially true if you add speed, loading, and repetition, such as during many exercises in the gym.
I spend a great deal of time discussing what “zones” of motion the person should be working in. Essentially, I try to develop a “green zone” and a “red zone” depending on when they have symptoms.
It’s important to continue working within their green zone and not simply say “take a few weeks off.” And slowly over time, our goal is to expand their green zone and reduce their red zone.
Treating Internal Impingement
Internal impingement involves a little more discussion. The main thing to realize with internal impingement is that this is pretty much a secondary issue. It is going to occur with any cuff weakness, fatigue, or loss of the ability to dynamically stabilize.
The overhead athlete will show some hyperlaxity in the “lay back” shoulder position of external rotation. Most overhead athletes have underlying laxity, what tends to happen is they lose strength or have an excessive workload that causes fatigue and then the structures impingement more and become irritable.
Treat the cuff weakness and its ability to dynamically stabilize to relieve the impingement. This often includes an initial period of rest and then building back their strength and dynamic stability.
How to treat internal impingement is a huge topic that I cover in a webinar for my Inner Circle members.
Learn Exactly How I Evaluate and Treat the Shoulder
If you are interested in mastering your understanding of the shoulder, I have my acclaiming online program teaching you exactly how I evaluate and treat the shoulder.
The online program takes you through everything you need to become a shoulder expert. You can learn at your own pace in the comfort of your own home. In addition to shoulder impingement, you’ll learn about:
- The evaluation of the shoulder
- Selecting exercises for the shoulder
- Manual resistance and dynamic stabilization drills for the shoulder
- Nonoperative and postoperative rehabilitation
- Rotator cuff injuries
- Shoulder instability
- SLAP lesions
- The stiff shoulder
- Manual therapy for the shoulder
The program offers CEU hours for physical therapists and athletic trainers. Click below to learn more: