4 Shoulder Impingement Tests to Differentiate from AC Joint Injury

How to Determine If You Have Shoulder Impingement or AC Joint Dysfunction

By Coach E

Shoulder pain can really throw you for a loop - especially if you aren’t quite sure what’s wrong or how to fix it. Read on to learn about shoulder impingement tests that will help you get back your aim, and your game.

Shoulder pain can really throw you for a loop – especially if you aren’t quite sure what’s wrong or how to fix it. Read on to learn about shoulder impingement tests that will help you get back your aim, and your game.

A Slow Build of Shoulder Pain

If you’re like most athletes with shoulder pain, it probably came on gradually.

Maybe you joined a baseball league and started pitching a couple of practices and games per week.

shoulder impingement test - baseball

A few weeks into the season, your shoulder really started to bother you. It would ache the day after a game and sometimes give you trouble when you’d try to hit the hay after practice.

You knew it probably had something to do with overuse from all the throwing, but you didn’t know much beyond that. And you REALLY didn’t want to quit halfway through the season.

So, you started trying to devote some extra attention to that achy shoulder.

You began a routine of static stretches, doing long holds before and after a game, trying to work whatever it was out.

You asked around to your buddies for advice, incorporating some exercises they suggested, kind of cobbling a regular routine together.

shoulder impingement test - fitness

Problem was, a few weeks went on like this and things just seemed to be getting worse.

The pain became more apparent, and it started to feel like each throw was playing with fire.

So what do you do now? Your attempt to heal your shoulder has served to only make things worse and prolong the pain.

This represents a common issue with shoulder pain – not really understanding what sort of injury occurred, and therefore not being able to effectively address it and move on.

Different Injuries, Different Approaches

Shoulder impingement – an issue in which tissues are compressed inside your shoulder joint – can often be mistaken for problems with the acromioclavicular (AC) joint, the joint at the top of your shoulder formed between the acromion process of your scapula and your clavicle.

 shoulder impingement test - shoulder bursitis

While these issues can both cause shoulder pain, they do so by different means and for different reasons (which you can learn more about in my articles on shoulder impingement and AC joint sprains). Because of this, they require different approaches to rehab.

It’s important to differentiate between the 2 injury types because what works for one won’t help heal the other. Having said this, no matter what the cause of your shoulder pain, it is critical to get to the root cause and establish a foundation for movement. And some techniques (like intense static stretching) probably won’t help either!

Symptoms – Similarities and Differences

The tricky part of differentiating between these 2 issues is that they can cause some similar symptoms.

For example, both shoulder impingement and AC joint injury can cause general shoulder pain and weakness that first is noticeable with movement, but starts to become constant as the issue worsens.

Overhead reaching or lifting movements are common pain triggers for both conditions, and as the pain becomes more constant, both can start to interrupt sleep when trying to lay on the injured side.

However, there are some symptoms that are unique to each issue and may help suggest that one or the other is at play.

AC joint injuries will often have a more centralized point of pain – right at the top of the shoulder where the AC joint is located. And depending on the severity of the AC injury, there might even be a hard lump at this spot [1].

Shoulder impingement, on the other hand, is more likely to cause pain over a wider area – potentially from the top of the shoulder all the way down to the elbow [2]. With shoulder impingement, you’re less likely to feel a really specific point of pain like that which is common in AC joint issues.

And while both problems can cause pain and weakness with overhead and lifting movements, each might also have a more specific trigger.

AC joint injury pain might also be triggered by a reach across your body, while shoulder impingement pain is more likely to be triggered by a reach behind your body.

Think about pain while reaching behind you to grab the seatbelt (shoulder impingement) versus pain when reaching across your body to buckle the belt in (AC joint).

Note from Dr. B: Impingement syndrome is a constellation of symptoms that includes pain over the top and outer aspect of the shoulder that are typically aggravated between 45-120 degrees of shoulder flexion and abduction. As Coach E describes, the symptoms are often activity related and intermittent at the start, but over time, they can progress and become constant, even preventing you from sleeping at night! There are many causes of impingement syndrome, essentially anything that decreases the space that the rotator cuff tendons travel. Swelling or thickening of the tendon that is damaged, inflammation of the bursa surrounding the tendon, or the development of bony spurs on the acromion and AC joint can all cause impingement. Remember, impingement syndrome is NOT a diagnosis, so you can have a normal rotator cuff with dynamic impingement, a partial tear or full thickness rotator cuff tear and experience the symptoms of an impingement syndrome. Sometimes a frozen shoulder will initially mimic an impingement syndrome, but the hallmark of a frozen shoulder is the progressive increase in pain in any range of motion with loss of shoulder rotation. Initial treatment will focus on decreasing inflammation in the bursa with ice or Nsaids. But the bottom line is we need to take the pressure off the rotator cuff tendons and AC joint to stop inflammation and the evolution of rotator cuff tears. So, get to the root movement issues, start with the exercises recommended in this article.

Dr. Erin Boynton, MD, FRCS.

shoulder impingement test - caution

4 Shoulder Impingement Tests

Beyond trying to differentiate between symptoms, triggers and pain locations, tests are a great tool for telling these injuries apart.

For some folks with either condition, their symptoms might just be general shoulder pain and weakness, which is not a great basis for a diagnosis.

By helping you examine specific movements and ranges of motions, self-assessments can help you take a more detailed look at your pain and provide some really helpful feedback.

Let’s take a look at 5 tests that will help you assess your injury so that you can better determine what went wrong and thus, how to fix it.

Oh and a quick note – I suggest you work through ALL of the tests, instead of just stopping after the first positive test.

Especially since these are self-assessments, it’s better to try them all and consider what the combined results suggested. This just helps you get a more firm idea of what’s going on in your shoulder.

#1: Hawkins-Kennedy Test

The Hawkins-Kennedy test is a classic shoulder impingement test that you can adjust to perform on your own [3].

Image by www.medicine.medscape.com

For this test, all you need to do is take the hand on the affected side and place in on the opposite shoulder (the shoulder with no pain). Your elbow should be bent and resting down toward your chest.

Now try to lift the elbow up, toward your face.

If this causes pain, it suggests that a shoulder impingement is likely behind your troubles.

#2: Horizontal Adduction Test

For this test, lift your arm up out in front of you to start. From here, take your arm across your body (horizontally adducting it).

sprained ac joint - horizontal adduction test

If this causes pain at the end of the range of motion, when your arm is really reaching across your body, it suggests that your issue lies in the AC joint.

In some cases, this test might cause pain for folks with a shoulder impingement, too [4]. (This is a great example of why it’s wise to do a few more tests to help see where the majority point you.)

#3: The Painful Arc Test

The “Painful Arc Test” is great because with this 1 simple assessment, you get both an AC joint test and a shoulder impingement test.

This test just involves 1 movement, but WHERE the pain occurs during the range of this movement can suggest either injury [5].

sprained ac joint painful arc test

To start, let your arm relax down by your side. From there, start to slow reach your arm up and overhead, or as high as you can manage with your pain.

Take note of where in the movement you feel pain.

If you feel pain in the middle of the range, from about 60 to 135° of abduction, a shoulder impingement is the probable reason for your pain.

But if you feel pain at the top of the range of motion – about 160 to 180° of abduction, your AC joint is the probable injury source.

#4: AC Joint Distraction (“Bad Cop”) Test

This next assessment, the AC Joint Distraction, or “Bad Cop” Test will clue you in to a likely AC joint injury.

To perform it, take the hand on the affected side and place it on your lower back, with elbow slightly bent.

(Think about how your arm would be placed if you found yourself in some trouble and were getting handcuffed. Whoops.)

Reach your left hand behind you to grab that arm right arm and pull it down.

If you have an AC joint injury, this movement will most likely cause pain at the top of the shoulder.

If on the other hand, you have an impingement, this movement is unlikely to cause you any trouble at all (unless you really are in trouble with the law).

What Next?

These tests should help clue you into what’s REALLY causing your shoulder pain.

With this knowledge, you can stop wasting your time with futile stretches or techniques that won’t help address the ROOT CAUSE of your pain.

If you tested positive for shoulder impingement on several tests, you’ll definitely want to check out my article on subacromial bursitis – a common underlying cause of shoulder impingement. This will help you understand the issue in-depth.

You’ll also want to take a look at my top 6 supraspinatus exercises. Weakness in the supraspinatus (a rotator cuff muscle) is also often tied to shoulder impingement, and devoting time to strengthening this muscle is a smart way to help your shoulder heal. The shoulder impingement exercises provided here are invaluable

subacromial impingement - acromion typesImage by www.shoulderdoc.co.uk/section/9

If, on the other hand, the tests seemed to suggest you might have AC joint dysfunction, head on over to my article on sprained AC joints to learn the 7 things you should do following these injuries.

Also check out this video on AC Joint pain:

Either way, make sure you don’t just stop after performing the tests…

Take the insight that these assessments gave you and APPLY it by becoming more informed on your shoulder health and likely condition.

This will help you get rid of that shoulder pain faster, and make it less likely that it will come back down the road.

About the Author

Eric Wong (aka Coach E) is the founder of Precision Movement and has a degree in Kinesiology from the University of Waterloo. He's been a coach since 2005 and spent his early career training combat athletes including multiple UFC fighters and professional boxers. He now dedicates himself to helping active people eliminate pain and improve mobility. He lives in Toronto (Go Leafs Go!) with his wife and two kids and drinks black coffee at work and IPAs at play. Click here to learn more about Eric.