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The Curious Case of Jacob deGrom


Before diving too deep into this post I want to say that I don't know everything that's going on with Jacob deGrom, I've never worked with him, and many of my observations and suggestions are just speculation. I do have a decent amount of public data as well as some anecdotal data and stories from his peers. Let's get after it.

DeGrom when healthy is one of the most dominant and electric arms in baseball. With a fastball that sears the mitt at 103mph, a slider that cuts through the fabric of time at 93mph, and a changeup faster than the average fastball at 94mph. This should be the stuff of a create-a-player, instead, it's a real-life human being and not a video game avatar. Unfortunately, we've only gotten to see a few years of this insanity before it started to slowly break down like a Ferrari that wasn't maintained. A ton of fun brand new, but if not taken care of it'll slowly break down into something that's only a fraction of its potential or worse, eventually totaled. So how do we prevent this? Let's first discuss the variables involved in this case.

I'm going to start with the most obvious issue in all of this, the injury history. DeGrom had Tommy John surgery in 2010 by Dr. Altchek, a standard reconstruction procedure. Following that procedure, he was pretty good until 2016. The real injury problem didn't begin until 2021. His public injury data looks like this.

  • 2016 - Ulnar Nerve Inflammation/Neuritis

  • 2016 - Ulnar Nerve Transposition

  • 2018 - Elbow Inflammation (Hyperextension)

  • 2019 - Elbow Soreness

  • 2021 - Latissimus Dorsi Inflammation

  • 2021 - Right Side/Low Back Tightness

  • 2021 - Forearm Flexor Tendonitis

  • 2021 - Shoulder Soreness

  • 2021 - Forearm Tightness/UCL Sprain

  • 2022 - Scapular Stress Reaction

  • 2023 - Elbow Inflammation

Those last couple of years have been something. The clear and obvious factor here is that he's overworking his throwing arm. The tissue breakdown is bouncing back and forth between the elbow and the shoulder. Now this is where I think some genetic factors start coming into play. DeGrom is listed as 6'4 180 lbs. He has a tall and lanky build that relies heavily on his long elastic levers to generate power. Now, I've never worked with him but from how it appears he's a very loose-jointed individual that I would classify as having congenital laxity which essentially means he was born with very loose connective tissue. Sometimes this is referred to as being "double-jointed".

Here's deGrom in the training room


You can see in the picture below how much horizontal hyperabduction he's getting into going into the late-cocking phase of the throw (bringing his scaps together). I'd bet the average human can't come close to getting into this position without pulling a muscle. This means the connective tissue is more "stretchy" which allows someone like deGrom to get back into extreme positions to leverage the most out of his body. You can gauge someone's laxity by doing a simple Beighton Test. Why does this matter you ask? Well, if the connective tissue doesn't have a ton of tensile strength and stability then the muscles will need to work double to protect the joint.


If we look back at the list of injuries he's racked up over the years we see some similarities. Most of these injuries can be linked back to increased laxity and hypermobility. 47% of asymptomatic individuals were found to have ulnar nerve instability at the elbow and 20-25% of individuals with ulnar neuritis have been shown to have subluxated or dislocated ulnar nerves. (Link) Elbow inflammation from a hyperextension injury is pretty self-explanatory. Then we start seeing some other variables in movement breakdown that we have to discuss.

A Latissimus Dorsi injury is a kinematic chain injury. It's a big muscle that must lengthen during the loading process and then fully activates as the arm crosses the midline of the body during the acceleration phase of throwing right before the release of the ball. This tends to do too much work when the small muscles around the scapula aren't controlling the movement enough and the Lat is then over-used to the point that the force the muscle absorbs goes beyond its structural integrity. This can be directly linked to hypermobility due to the lack of muscle control and stability around the joint.

He then bounces back and forth between the elbow and shoulder which is sometimes a sign that the body is trying to compensate to avoid injury which then causes another area to take too much force and then break down again. It's ping-ponging back and forth until he finally overloads the UCL and is officially diagnosed with a UCL sprain which is a big deal because if you remember he had UCL reconstruction in 2010. What we haven't talked about much yet is that his pitching mechanics could be a major factor in why he's breaking down in certain areas. Movement mechanics are a direct response of force activation, force vectors, muscle and connective tissue force absorption, and overall stress to a region. We'll discuss this more later.

The big injury that points to deGrom having a serious issue with muscle activation and stability happened in 2022. A scapular stress reaction is a stress to the bone which causes a noticeable stress response called a periosteal reaction. This is the phase right before a stress fracture, which is a microfracture in the bone. A stress fracture is the stage right before a total fracture which is a really big deal, especially when it comes to a floating bone like the scapula. There have only been a handful of diagnosed scapular stress reactions in professional baseball. Edwin Correa in 1987 was the first, then Kurt Ainsworth in 2003, then more recently Brandon McCarthy in 2007, and Michael Wacha in 2014. The two most recent ones have several similarities to deGrom. They're all tall, lanky, incredibly mobile, and loose-jointed individuals. The mechanism for this injury is described as an overload of repetitive force from the muscle to its boney attachment. The muscle tugs and tugs and tugs which causes that periosteal reaction to start flaring up. If all of the muscles don't coordinate together as the arm goes from fully loaded/late cocking phase to ball release and deceleration then only a few muscles are responsible for the stress of the movement. Again, this goes back to muscle coordination and stabilization. Something that's interesting, and I can't totally confirm this, but one of these individuals had their stress reaction in the middle of the scapular where there's not a true rotator cuff insertion at the point which kind of throws out the potential theory of the muscle pulling on the bone to create that stress response. So what is happening? Well, when stress fractures occur in the foot in runners it's due to the stress absorbed by the bone from repetitive landing or jumping. So in a situation like this, I speculate that there's a potential that these incredibly loose-jointed individuals are able to retract and load their scapula in a position that puts a ton of stress on the scapula in a similar way that runners develop stress fractures in their foot. It's as if they're loading their scapula against their ribcage and using that to jump off of as they go into acceleration and ball release. If you go back to the picture above you can kind of see how this is possible. If you do this over and over to the scapula it creates a similar stress response as if you bend a wire hanger over and over until it starts to deteriorate.

We now need to discuss pitching mechanics and their potential involvement in this repetitive breakdown. He's publically talked about how he's always tweaking and working to optimize his pitching mechanics(Link).

In this video from 2020, you can see his timing with his throwing arm going into foot-strike and acceleration is relatively clean. The one thing you can't really tell from this angle is the pull from his glove side creating what's called "early trunk rotation" which he talks about being an issue of his. When the glove pulls around it's actually starting to create tension in the throwing shoulder even before the front foot lands on the ground. When the arm is late it puts more stress on the shoulder/scapula and its connecting musculature. When you're already hypermobile you're not going to be utilizing the muscle stability around the joint, so combine more end-range stress and leverage of the connective tissue and bones and you'll get a damaging response. What can also happen is that the body starts compensating as things start breaking down and it shifts the stress to different structures later down the chain (ie the elbow). Mechanics can be an important factor in repetitive overuse injuries which is the majority of injuries that occur to pitchers, but his aren't as seemingly bad as others. This is where things get interesting. Just because someone appears to move well on video or even an advanced 3d motion capture assessment it doesn't necessarily mean that they're moving well. Both of these examples have no clue on how the individual is activating their muscles to create force and stabilize to protect from compressive and distractive stresses. It (3d motion capture) has no ability to detect the amplitude of activation of specific muscles as well as the timing of these muscles during the pitching motion. This in my opinion is more important than anything else! It's why you see some pitchers with what appear to be "horrible" mechanics stay relatively healthy longer than most expect. Some pitchers control their body and their ability to stabilize much better than others. It's internally the protective mechanism and kinematic sequence that most try to achieve but not even x-ray vision would be able to tell you. Currently, the only true way to have some idea if this is going on is to have someone who knows how to assess muscular stability, coordination, and functional patterns, specifically in pitching mechanics. I'm not going to break down his mechanics too much more because my buddy Ben Brewster did a much better job here.

So we've delved into his injury history, his genetic makeup, and his pitching mechanics, but now we need to discuss what I believe could be a career extender for him. Like I was saying earlier, deGrom has a ton of laxity in his joints and needs more muscular stabilization. Let's dig into this more.

We've talked about how he's overloading certain muscles more due to his laxity and the leverage he gets in getting his joints into a deeper end-range which generates more power. This creates a joint "decentration" event, which essentially means that the joint has uneven loading on the bone and connective tissue structures due to an imbalance of muscle activation around stabilizing the joint.

You can see in the picture above that the shoulder on the right is a decentrated joint where the short/tight muscle is pulling the humerus more up and into the joint because the lengthened/inhibited muscle isn't doing its part to keep the joint balanced. The result of this is uneven joint surface loading, which creates a loosening of the bottom side of the capsule and a buckling of the top of the capsule. Now, this is a clear exaggeration but the stress effect of this is occurring. Take this effect into consideration with deGrom who is loose-jointed and you have even more stress around the joint due to the forces and end ranges he's getting into.

So how to we centrate a decentrated joint? Great question! There are a few factors we must consider such as which muscles do we need to strengthen to create that balance, which muscles do we need to reduce some of the tone/tension in, and what's the best setup or technique to accomplish this task. The problem with the majority of strength training and rehab plans is they follow standard training guidelines and ideologies. The shoulder is a problem? Strengthen the rotator cuff. Do it with open-chain banded work. Trying to get the Serratus Anterior more involved? Do some form of push variation using a foam roller on a wall. This doesn't really get the job done. The majority of these involve open-chain setups which is a problem because the brain will want to use any resource it can to get the job done. It will over-recruit the short/tight muscles that the individual typically compensates to which we discussed in talking about joint decentration. They achieve the desired result when we take them into a closed chain position where you can turn off the need to recruit the typical muscles they compensate to. There are different ways to achieve this, but I primarily use DNS positions and principles to get the job done. Why? Because I can put someone in a cross-crawl position which is contra-lateral in nature (meaning cross-body) and I can get them to turn off the compensatory patterns in these closed-chain positions. There is a lot more we can discuss about trigger point patterns and neurologic tension, but that's probably for another time. This is getting lengthy.

Once you have the tools necessary it's a pretty simple formula:

Soft tissue work to loosen the neuromuscular muscle and joint tension


Stabilize the joint by activating the little intrinsic muscles while having the compensated muscles turned off


Better functioning joint with proper joint centration which means less strain to certain areas and better-shared stress

The brain is incredibly plastic and can learn new movement patterns even as we age, but the way in which it's done is important. Constraints alone won't be able to change the compensatory patterns that throwers develop. They have to learn to move better before the constraints are added otherwise you build variability on a less-than-ideal moving system. This same approach can be used throughout the body, not just the shoulder. This is how we achieve optimal movement both from a medical perspective and a performance perspective. The fun part is combining the movement pattern change with the pitcher's body style and pitching style to optimize how they move.

Let's wrap this up. I think deGrom is a once-in-a-generation pitching talent that has the capability of pitching to his prime for another 3-6 years in the big leagues. The problem is if can he do this without major compensatory breakdown of his body every year. Repetitive overuse injury is the most common reason a pitcher falls apart. He has a unique body style that requires a unique approach to improving the likelihood he can both stay healthy and perform at his performance level. He has a real shot at a hall-of-fame career, but he has to get this right immediately. I personally know the Rangers have people on their medical staff that have the ability to do what we discussed, but the issue is whether they are allowing them to do what's necessary or if deGrom is allowing anyone to help him through this. It's a curious case indeed. It's the question I get asked the most about by other big leaguers. "What's going on with deGrom?" Well, this is what I believe is going on. If someone in deGrom's camp or deGrom himself reads this, feel free to reach out. I have plenty of references from your colleagues that would agree it's exactly what you need.



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