Shoulder Impingement Syndrome: Is It a Bone Problem That Needs a Surgical Solution?

Fixing Shoulder Impingement and Its Attendant Pain Means Taking a Closer Look at Your Functional Movement—Not that Your Bones Are Built Badly

Table of Contents


A Quick Overview of Shoulder Impingement 

Surgeons often claim that shoulder impingement syndrome (also known as subacromial impingement) is the result of bad bone shapes. This theory was first introduced in 1972 [overview by the Journal of Bone and Joint Surgery available here] by surgeon Charles S. Neer II. He had dissected cadavers for evidence of rotator cuff tears and proposed that there was correlation with acromion shape.

The theory is that the acromion, the end piece of your shoulder blade, rubs against the top of your rotator cuff tendons and causes fraying, damage, and pain. According to conventional orthopedic theory, there are three general types of acromions: I, II, and III. 

Type I is considered “normal.” 

Type II and III are considered to be at higher risk for subacromial impingement. 

To fix the alleged structural problem in types II or III, you could get an acromioplasty, a procedure in which a surgeon reshapes the bone. In theory, this gives it a “better” shape that is less likely to rub the top of your rotator cuff tendons. 

If this theory were true, we would expect:

  1. type II and III acromions to be strongly correlated with shoulder impingement
  2. acromioplasty to yield good results and solve shoulder pain problems

In reality, we do NOT observe either of these phenomena. In this article, we'll dig into some of the relevant research around shoulder impingement and shoulder impingement surgery. We'll also see why one outspoken orthopedic surgeon fervently believes you can avoid the overwhelming majority of shoulder impingement surgeries.


 Watch this video for a fantastic breakdown of Shoulder Impingement Myths and Realities


How Acromion Types Are—or Are Not—Related to Shoulder Impingement

Let’s start with acromion types and rotator cuff damage. A 2002 study searched for an association between acromion type and rotator cuff pathology. In its summary, the researchers state, “Stratified univariate analysis revealed no significant association between acromion morphology and rotator cuff pathology in patients who were over 50 years old.”  

In plain English, that means the study found acromion type was not correlated with rotator cuff pathology in this age group. 

Now what about allegedly bad acromion types? 

In a 2010 study researchers looked at 305 people 21 years and older who were asymptomatic with no history of shoulder problems.

They found that—in this asymptomatic population—81.3 percent had type II acromions and 14.1 percent had type III acromions. 

Look at those numbers again. Given 95.4 percent had either type I or II acromions, that means only 4.6 percent had the allegedly “normal” type I acromion. If type I is supposed to be normal, how could it make up such a tiny fraction of the asymptomatic population? Type II and III acromions are the majority, with type II being the most prevalent by far. 

If type II and III acromions indeed are the bad bone shapes, we would expect to see the asymptomatic population skew heavily toward type I acromions. And we should see a statistical association between the acromion types and rotator cuff pathology. But we don’t.

Finally, in a 2018 study, researchers found no correlation between acromion shape and rotator cuff tears in 227 subjects. If acromion shape is a major cause of impingement pain and rotator cuff tears, these results wouldn’t make any sense. 

In their summary,  the authors noted the shortcomings of the “bad acromion type” theory: “Neer and Bigliani reported that the Type III acromion type is closely related to [rotator cuff tears]. However both studies were based on only small cases of cadavers, not live human beings.” 

And in their conclusion: “we have proved that age is the most powerful predicting factor whereas acromion type had no significant relationship with supraspinatus tear and multiple [rotator cuff tears].” 

Also important to note is that the Journal of Bone and Joint Surgery even remarks: “Neer believed that impingement causes rotator cuff tears. This hypothesis does not appear to have withstood the test of time. It is more likely that rotator cuff dysfunction results in upward displacement of the humeral head and causes impingement of the humeral head against the acromion with shoulder use rather than the reverse.”

In other words, they’re saying that the contemporary theory is that rotator cuff muscles that aren’t working right result in poor movement patterns that cause the upper arm bone (your humerus) to hit the acromion. 

These publications should make anyone strongly question the “bad bone shape” theory of shoulder impingement. If even the Journal of Bone and Joint Surgery is no longer pushing the idea that acromion shape relates to the development of shoulder pain, it’s probably time to abandon it. 

The Journal of Bone and Joint Surgery continues: “The liberal use of acromioplasty to treat 'impingement' is being replaced by a trend toward making an anatomic diagnosis, such as a partial or complete tear of the rotator cuff, and performing corrective surgery such as repair of the torn rotator cuff.” 

In other words, they attempt to find a structural problem and fix it surgically in the hopes of improving the shoulder movement patterns. This structural approach to “fix” the human body is a classic orthopedic strategy that doesn't seem to pan out when put to the test in placebo-controlled trials (which we’ll see in a moment). 

See also: Why you DON’T Need Orthopedic Surgery for Joint Pain



Does Shoulder Impingement Surgery Work? 

Before we dive directly into shoulder impingement surgery, it’s important to take a look at orthopedic history. There are several examples of surgeries being introduced and popularized without adequate evidence that they are effective and worth the downside risks of infectoin and other complications. When researchers eventually scrutinized the underlying theories and surgical outcomes, they found the benefits of these surgeries were oversold, since fake surgery or other nonsurgical approaches were just as effective. 

Knee meniscus surgery is one example. However, long-term follow-up on a randomized controlled trial has shown that knee meniscus surgery has the same effectiveness rates as placebo surgery. “There was a consistent, slightly greater risk for progression of radiographic knee osteoarthritis in the APM group as compared with the placebo surgery group”  

The same is true for knee surgery to allegedly treat knee osteoarthritis. In a 2002 paper published in the New England Journal of Medicine, fake placebo knee surgeries performed just as well as real knee surgeries.

And despite decades of strong claims of effectiveness and superiority to nonsurgical treatment, spinal fusions have turned out to be no better than nonsurgical alternatives in multiple studies.

The great news here is that researchers have already done placebo-controlled studies on shoulder impingement surgery (subacromial decompression), so we have solid research to look at. 

A 2017 study published in the Lancet showed that there was barely any difference in outcome between shoulder impingement patients who had surgery, fake surgery, or no treatment at all. 

They found patients who received no treatment at all scored only slightly worse than the patients who had placebo or real surgery. The difference, according to the authors, was not clinically significant. 

In addition, the placebo surgery was just as effective as the real surgery. 

The researchers state: “The difference between the surgical groups and no treatment might be the result of, for instance, a placebo effect or postoperative physiotherapy. The findings question the value of this operation for these indications, and this should be communicated to patients during the shared treatment decision-making process.”

In other words, like knee meniscus surgeries and spinal fusions, shoulder impingement surgery appears to be more hype than hope. 


How Can You Fix Shoulder Impingement without Surgery? 

When you have problems moving your body parts, you need to focus on the organs of movement: your muscles. Regardless of the shape and condition of your bones, they cannot and do not move themselves. This is the root of the mantra I repeat in many of my YouTube videos: ATM (Always Think Muscles!).

Muscles move bones. Muscles determine bone position. So if we want to have pain-free range of motion, we need to retrain muscles to move the bones properly. If muscles are not balanced in terms of flexibility, strength, and mobility all around the scapula, ribs, spine, and shoulder joint, the shoulder can’t function smoothly. This is why orthopedic surgeon John Kirsch strongly recommends exercise instead of subacromial decompression.

In the video below, I demonstrate and explain five exercises that can help you restore function to your shoulder.

It’s important to recognize that every person has specific movement patterns that are the result of daily habits, frequent movements in work or sport, and compensations for or direct effects of injuries.

The free video above is a good starting point.

If you want a more comprehensive program to retrain all the muscles around your shoulder, be sure to check out the Shoulder Fix program.

For years, I was unable to lift my arm out to the side or in front of me without pain, snapping, and popping in the joint. It took me years to realize that I could fix the problem myself. As I was solving that problem (and many others with my body!), I started helping others with their problems.

The Shoulder Fix is a program designed to help you with your shoulder problems. Impingement is just a way to say that your muscles need help, and with the Shoulder Fix, you can learn step-by-step how to help them!

Train your body to be more flexible, strong, and resilient! 

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