Internal rotation deficit in overhead athletes. Do not assume it is the posterior capsule. Think outside of the box!

I can’t begin to tell you how many times I have heard clinicians that work with over-head athletes saying that their athlete needs the posterior capsule of his shoulder to be stretched after they have been diagnosed with GIRD (Glenohumeral Internal Rotation Deficit). GIRD is one of the most popular “issues” with overhead athletes and, nine out of ten times, the posterior capsule is blamed for the loss of internal rotation and preventive stretching with strengthening programs are given to the athlete to improve this motion in order to decrease the risk of injury.

One big problem with this concept is that GIRD is telling you a finding on examination, not the cause for the loss internal rotation. When someone is diagnosed with thoracic outlet syndrome (TOS), we know what the finding is, but we still investigate the cause. Same concept should apply to GIRD, but that seems to be forgotten in most clinicians that deal with such finding. To improve the outcomes of our patients, we should be able to find the cause of the internal rotation loss to be able to provide the best plan of care. I am not saying that the posterior capsule isn’t ever the cause of the loss of internal rotation, because it could be. What I am saying is that there is more than one reason for GIRD to occur and us, as clinicians, should be able to detect the cause and develop our own personal evaluation method for the assessment of this adaptation in the overhead athlete.

After my experience in professional baseball for 11 years and currently working with the ATP world tennis tour for a year, I can tell you that the evaluation of the glenohumeral joint is not simple at all. I can also say that the posterior capsule isn’t the most common cause of internal rotation loss. Hopefully after reading this blog, I can get you to think a bit more outside the box and not fall into the trap of stretching the posterior capsule immediately.

·       Why is this important?

There is a high correlation between GIRD and shoulder injuries in over-head athletes. It has been researched and published in the literature for many years now so we should pay attention to it. However, research has evolved in the past few years and the original finding that we thought it was the predictor of injury, may not be the main driver after all. We should be careful with the finding of GIRD in overhead athletes and interpret what we find in examination based on the latest evidence in the topic.

Like stated before, GIRD is an examination finding that has been automatically assigned to a posterior capsule tightness. However, this hasn’t been proven true in all cases of GIRD. There is research evidence showing that some over-head athletes show greater posterior translation of the glenohumeral joint than anterior translation. Would this be possible with a tight posterior capsule? We can argue yes and no for this question, but wouldn’t we need more information to help us find the answer? So, what do we do?

Let’s start with what normal shoulder motion in an overhead athlete is, so then we can move to pathological reasons of why GIRD occurs commonly and how can we identify them.

·       What is normal?

There is enough research out there than can speak to the glenohumeral adaptations from the stress demands of over-head activities in athletes. The most talked about one is GIRD, which is a decrease in IR (internal rotation) of the shoulder of about 10-15 degrees compared to the opposite shoulder. What it is not common knowledge, is that with the lack of IR there is a subsequent increase in ER (external rotation) compared to the opposite shoulder. However, if you look at the total motion of the shoulder (ER +IR)  both shoulders are usually equal bilaterally or within  a 10-degree difference. We call this a shift on the total arc of motion. This was best  described by one of my mentors Mike Reinold in the illustration below.

This raises the question, should we be worried about the lack of IR or the excess amount of ER?

HERE is an illustration from Mike Reinold’s website that explains this adaptation.

On the left you see a non-over head athlete’s total ROM and on the right,  you see an over-head athlete total ROM. If you add up the numbers, total arc is still 180 degrees. However, in the overhead athlete, it has shifted more “to the external rotation side”. This is a phenomenon that has been shown in several publications (Wilk CORR 2012, Meister AJSM 2002, Reinold AJSM 2008).

This is a normal adaptation shown in over-head athletes. Therefore, just because it is found it doesn’t mean it is pathological. Over-head activities are extremely stressful on the glenohumeral joint that it would be impossible not to find adaptations from it. What I consider (and a lot of other researchers in the topic) pathological will be described at the end of the blog.

·       So why does this happen?

Here is where the fun part begins. There could be multiple reasons, which we will explore, but the most common reason given by physician’s, Physical therapists, and Athletic Trainers unfortunately is tightness to the posterior capsule specially if the internal rotation is less than the non-dominant shoulder without considering changes in total arc of motion. In fact, true loss of IR due to a posterior capsule tightness is one of the least possible causes for GIRD in my experience.

Let’s start with simple biomechanics. The posterior capsule limits three osteokinematic motions: Internal rotation at 0-45 degrees of abduction, flexion, and horizontal adduction.

Once the shoulder goes to 90 degrees abduction, where most overhead athletes performed their sport activities, internal rotation is mostly limited by the posterior band of the inferior GH complex. This is important because most people test internal rotation at 90 degrees abduction to diagnose GIRD. In that position, the posterior capsule goes on slack, and not really being a participant in restricting the motion. Therefore, to get you thinking outside of the box, why would we jump into treating something we aren’t even testing?

The picture HERE illustrates the tissue restraints for IR at 90 degrees abduction.

Unless there is a restriction in all the three motions mentioned above, with an additional hypomobility in posterior glide of the shoulder with the scapula stabilized at 45 degrees abduction, there is no reason to suspect the posterior capsule is responsible for the loss of IR based on simple biomechanics.

Moral of the story is: Do not assume the posterior capsule is tight with just one test, especially with one test that doesn’t even biomechanically puts stress on it.

Another matter to think about is histology. The collagen composition of the IGHL is thickened bands of well-organized collagen bundles that resist motion in one direction only, just like any other ligament (think of ACL). So, let’s think about it for a second. Do we really want to crank the shoulder in internal rotation to stretch the posterior band of the IGHL that is a main stabilizer of the shoulder posteriorly? Do we ever stretch an ACL or an MCL?

·       If its not the posterior capsule, then what is it?

Another reason for lack of IR could be a normal bone adaptation called retroversion. This is a very well study phenomena that can explain the shift in humeral total arc of motion when compared bilaterally. Retroversion specially occurs when you participate in overhead activities in adolescent years and your growth plates adapt to the torque stress given by the sport. This retroversion happens at the humerus and the glenoid. The amount of retroversion seeing in overhead athletes is about 10 degrees, which is the average loss of IR compared to non-dominant arm.

This can be measured clinically. My mentor Mike Reinold developed a way to assess it that is very quickly and effective. For more details, see: measuring humeral retroversion.

Another way to clinically see if someone has retroversion is subjective. When stretching someone in a 90-degree abduction position into internal rotation, someone with increased retroversion will have a hard end feel at the end range of IR. You will also notice how the shoulder migrates anteriorly when that hard end feel is felt. This should raise the suspicion of bone-on-bone contact of the greater tuberosity and the glenoid. The picture HERE show this bone on bone contact, but you can see how far anteriorly the greater tuberosity is when fully internally rotated. If there is a 10-degree retroversion in the humerus, it could potentially hit the anterior part of the glenoid rim.

So, do you think that stretching the posterior capsule will help if retroversion is the cause of IR loss?

·       What about soft tissue (besides the posterior capsule) causing a loss of IR?

Overhead athletes, besides their retroversion adaptation, develop muscular imbalances that can alter the amount of motion (in the case of this blog, internal rotation) in the shoulder. The rotator cuff acts as a decelerator of the arm during the end part of the throwing motion. The forces necessary to decelerate the arm are tremendous, which puts a lot of stress in these muscles. Because of that, they tend to get chronically short as an adaptation to the stress. There is research that speaks about the loss of IR of a pitcher acutely after a game, and even gradually during the season. Chronic shortening can lead to muscle weakness, which is also common in overhead athletes. This weakness creates compensations, most specifically in the bigger muscles like upper trapezius, that will elevate, anteriorly tilt, and rotate the scapula upwardly, putting the rotator cuff in an even more shortened position, decreasing the IR range of motion.

So how do we know if the rotator cuff is the cause of the loss of IR? Very simple. Assess the amount of internal rotation before and after some soft tissue treatment to the rotator cuff. If the increased in temperature and pliability from the soft tissue treatment restored IR, then you shouldn’t be concerned that the posterior capsule is affecting the motion at all.

·       What about the kinetic chain?

We are all very familiar with the role of the proximal and distal extremities in injuries, that is why we screen the cervical spine and the elbow when performing a shoulder evaluation. Is there a possibility that the spine could limit IR?

The answer is yes

There is well known research establishing the role of the thoracic spine in limiting shoulder movement. There is a direct correlation between a lack of thoracic extension with shoulder elevation, as well as decreased thoracic rotation and laxity in the anterior shoulder joint in the ipsilateral side.

So, how does that translate to a decrease in IR? With an increased kyphotic posture, most commonly found in overhead athletes, the upper ribs where the scapula is set have an increase in anterior rotation to accommodate the excessive kyphosis of the thoracic spine. The scapula, must anteriorly tilt as a compensation, creating soft tissue compensations like pectoralis major tightness, tight latissimus dorsi, tight upper trapezius. All these compensations can create non-structural retroversion of the humerus  and limit IR (same as structural retroversion talked about above).

Would stretching the posterior capsule do anything for this problem? Should we focus instead on the soft tissue that is compensating for the T-Spine and see if that improves internal rotation?

The answer is yes.

·       Why is finding the cause of GIRD important

We all want what is best for our overhead athletes, or any athlete in general with an injury related to a lack of motion in the shoulder. Therefore, it is necessary for us to get to the real cause of the lack of mobility (in this case IR) to treat it more effectively. If the problem is a rotator cuff spasm due to weakness, why would we assume the lack of internal rotation is the posterior capsule and stretch it? Doing so will create a separate instability than what is already present in most of these athletes anteriorly and could potentially bring more problems down the road. Same thing if the reason for a lack of motion is the thoracic spine. Appropriate evaluation and treatment are key.

·       Is GIRD even significant?

GIRD has gotten so much attention that there are multiple rehabilitation and strength and conditioning programs out there to reduce this finding. It has a negative connotation in a lot of health professionals, but as we saw it can be an anatomical variation observed in overhead athletes.

So, is GIRD even the cause of injuries?

As we learned earlier, the total arc of motion in people with GIRD does not change, it only shifts. So, how are we sure that the decreased IR is the problem and not the increase in ER?

The answer is that we aren’t sure. We just decided to blame IR because it was the movement that was lacking, and it is easier to mobilize something that is tight. There is no evidence as of today that says the decrease in IR is the reason for injuries over the increase in ER.

We all know that with increase mobility, the demands for stability need to increase as well. If our external rotation has increased, our rotator cuff strength and stability should as well. But how many times we find overhead athletes with rotator cuff weakness? Wouldn’t this cause excess movement in the joint that could lead to impingement?

I’m not saying that a lack of IR isn’t a problem, because sometimes it can be the problem of a specific athlete having an injury. For example, if the true cause of GIRD is the thoracic spine and an anterior tilt of the scapula, this can cause shoulder impingement as well.

So, the point of this blog is to make you think next time you treat an overhead athlete that lacks IR. Assess and don’t assume. If you have an overhead athlete with a shoulder injury do not base your decision on GIRD, but on total motion instead compared to the non-dominant side.

In my experience of treating hundreds of baseball players, everyone is different, and such should be treated differently.

So, what is the magic number? From previous research and other colleagues work, anything above or below a 15-degree difference on total arc of motion between dominant and non-dominant arm should be assessed.

It is easy to blame the lack of IR commonly known as GIRD on a tight posterior capsule. However, as stated above, there are multiple things that can cause a lack of IR that need to be assessed and treated before creating an unnecessary instability in the joint, where there is one already present. Not all shoulder injuries in overhead athletes are caused by GIRD, as there is no research stating that the decrease in IR has a cause and effect relationship with injury. With that decrease in IR comes an excess in ER, which can also be guilty of increasing the risk of injuries. It is important for us to assess if the total arc of motion is pathological via a total arc of motion increase or decrease compared to the non-dominant side so we can prescribe the best treatment plan for our patients.

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