Shoulder impingement is the most common and most misunderstood shoulder conditions we have. I see it in the clinic often, and the challenge is it describes the action that causes pain, not the actual source of pain. I’ll discuss that, the different types of shoulder impingement, how to manage it, and what to expect for healing.

Shoulder Impingement symptoms

Common complaints with shoulder impingement are:

• Reaching over head, in front, or across your body
• Throwing motions, reaching behind you, or putting on a shirt/jacket
• Pain on the front of the shoulder or radiates down the arm
• Unable to sleep on the that side

Diagnosis and Types of Shoulder Impingement

There are a bunch of special tests to assess your shoulder and help diagnosis the TYPE of impingement you have, but they aren’t very specific.

To diagnosis shoulder impingement, you tell me “my shoulder hurts when I do XYZ.” I then perform tests that closely mimic XYZ. You say “OUCH,” making the test positive.

Your history (location of pain, activities that hurt, recent changes in activity) are the most important since they will dictate which tests I use to confirm what I think is wrong with you.

Shoulder impingement only highlights that pain is present, not what in the shoulder actually hurts. To understand this, you have to understand the 2 types of shoulder impingement:

1. External (primary and secondary)
2. Internal

External Impingement

Since shoulder impingement is not specific, the new term is Subacromial Pain Syndrome. The acromion or coracoacromial ligament is compressing a structure (bursa/tendon) under (sub) the acromion. You feel pain because that irritated structure gets smooshed, exactly how a bruise works.

Shoulder “impingement” ALWAYS occurs, even in pain free shoulders. That red spot is the subacromial space.

There are 2 types of EXTERNAL Shoulder Impingement

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Primary External Impingement

Primary means a structural cause. A common thing to blame is acromion type. You can see in the not realistic cartoon sketch below there are 3 types. Notice Type III has a scary looking hook making the space more narrow, making it easier to compress the tissues.

It looks scary too since it’s basically a hook straight out of a horror movie slashing your rotator cuff. Rest assured that is NOT happening.

The issue of acromion type is debated for a few reason. One, there’s no good way to measure it since humans don’t look like cartoon drawings. Imagining isn’t good enough, and actual scapula position (which can vary person to person or standing vs. sitting vs laying) can change the angle.

Oh yeah, and the margin of error of the measurement device can be larger than the recorded differences of the types.

Two, cuff tear severity is not related to acromion type. You can have a massive cuff tear with Type I, or a small tear with Type III (on the off chance you can ACTUALLY tell the acromion type!) This is true with progression too, type does not mean slower or faster degenerative progression.

Third and final, you don’t have a choice since it’s possible your type is predetermined. They did a study where they looked at a bunch of shoulders and saw a variety of types, so they thought it changed over time.

Then they did a study where they looked at a bunch of the same shoulders over 3 years and none of them changed. It’s possible 3 years isn’t long enough.

Basically we don’t know shit.

It’s likely all related to overall rotator cuff muscle quality. So, you know, you should exercise.

Secondary External Impingement

Secondary is related to impaired strength and mechanics of the cuff muscles and the scapula muscles. So, you know, you should exercise.

Both primary and secondary shoulder impingement likely have strength and ROM deficits, secondary won’t have (as much?) associated structural stuff. Makes sense since Primary is the most common and usually affects older (> 40yo) folks.

The longer you are alive, the greater chance to get all these things. Another argument for tissue quality. So, you know, you should exercise.

Internal Impingement

This is impingement in the back of the shoulder and it is common in throwers, i.e., baseball pitchers. Makes sense right, throwing a baseball really hard requires a lot of shoulder ER (range of motion BELOW the table), so people that throw baseballs really hard will have a lot of shoulder ER.

You may also have reduce ROM overhead and the front of your shoulder can be “loose” to allow that much extra ER ROM. This can later lead to a cuff tear or labrum issues.

Internal shoulder impingement pain is felt in the back of the shoulder (left picture) in the late cocking phase of throwing or putting on a jacket.

I’ve currently treating a 17 yo female in the band and a 43 yo male fighter pilot that have ROM just like the baseball player picture above. The female’s symptoms are NOT consistent with internal impingement, the pilot’s are.

Treatment of Shoulder Impingement

Treatments for each all involve the same thing – treat the impairments. Examples of impairments include:

1. Pain – oscillations, soft tissue work, isometrics
2. Improving shoulder mobility
3. Strengthen the scapular rotators

Do these exercises at a lower intensity to promote healing and blood flow. Otherwise, you’re just irritating whatever is irritated. Over time, you slowly increase the intensity of activity to increase tolerance.

Prognosis and What to Expect

Healing is the hard part, especially since it usually involves tendons that go through specific stages of healing. Tendons don’t have as good of a blood supply as muscles, so it can take longer.

Standard for any soft tissue injury is the default 3-7 weeks with tendinitis, and more chronic type stuff like tendinosis can take 3-6 MONTHS and require long term maintenance.

One thing to keep in mind is that pain is not a good indicator of what’s going on in the tissues. You can have no pain but the tendon has low tolerance, so as soon as you start pushing the intensity (heavier weight, faster speed, etc), the pain can come back if you exceed your tolerance.

Summary

That wraps up the basics on shoulder impingement. The diagnosis just tells me you hurt, not WHAT hurts. Often it’s related to overloading some tissues beyond what it’s capable of tolerating. Healing can be slow, so the goal is to treat the impairments (pain, ROM, strength) as things heal. Over time, your tolerance will improve.