Everyone involved with the Yankees understands that the individual contributions of Corey Kluber are going to go a long way towards determining the level of success the Yankees have on a team level this season. Surely no one expects him to be the Kluber of 2017 when he led the American League in eight major categories and won the AL Cy Young award. But if the Yankees get 160 innings with a slightly better than league average performance from him, that would be a big boost to a rotation that has several question marks.
Can Kluber remain healthy enough to be a plus contributor throughout the 2021 season? Like every other issue with bio-mechanics, the answer is, “it depends”.
Discussing shoulder function as the end result of an action that uses six hundred plus muscles that combine to use two hundred plus joints to throw a baseball powerfully and accurately is far too expansive for a post such as this. For the purposes of brevity, I’m going to oversimplify some complex issues. That said, to paraphrase Russell Carelton of Baseball Prospectus:
Warning: Gory bio-mechanical details ahead!
Kluber’s future health largely depends on whether or not the cause of his shoulder problem can be identified and addressed. For example, a knee problem is rarely a knee problem – quite often it’s a lack of mobility and/or function in the ankle or hip which leads to stress on the knee. A low back problem is rarely a low back problem – typically it’s a lack of mobility and/or function in the hips or mid-upper back which leads to stress on the lower back. The site of the pain and injury are usually just the symptom and end result of dysfunction elsewhere. And as in every other aspect of life, a problem can’t be fixed until the cause of the problem is removed.
In Kluber’s case, his shoulder – specifically the tear in his teres major muscle – was likely the symptom and end result of a dysfunction elsewhere, which forced excess stress on the shoulder. If the issue that caused stress on the teres major can be identified and improved, then there’s reason for optimism.
The shoulder is an extremely complex set of joints that needs to be very mobile in order to function correctly. The problem is if it becomes too mobile, there are going to be muscle, tendon and/or ligament problems as a result.
What could cause excess mobility in the shoulder that would lead to injury? Many, many things, but one possibility is elbow dysfunction. If the elbow isn’t functioning correctly, it’s not uncommon for the shoulder to increase mobility to cover for the elbow problem. (Remember, the shoulder is at one end of the humerus bone, the elbow at the other – if one end is moving incorrectly, the other end will move incorrectly too.) So an elbow with altered movement may cause the shoulder to over-compensate and alter its movement, eventually leading to stress in the shoulder.
What could lead to a change in elbow function and movement? Many, many things, but a fracture to the forearm, for sure. When we are injured, our body changes our movement to avoid pain whether we realize it or not. It’s not uncommon for peoples’ gaits to change permanently after spraining an ankle – the body alters the walking pattern to avoid pain, usually subconsciously, even after the pain subsides. So it’s not unreasonable to think that a broken forearm, which is quite painful – could and would alter movement and function at the elbow, even if only slightly, even after the pain is gone.
I’m sure you know I’m not choosing the ulna bone in the forearm randomly, as Kluber’s was broken by a line drive in 2019. It certainly isn’t crazy to think that the broken ulna slightly altered the movement and function of the elbow, which in turn slightly altered the movement of the shoulder, which could have contributed to altered function and injury in the teres major.
To be clear: I’m not saying that’s what happened. I’m using it as an example because it’s one of many possibilities. Kluber also mentioned stiffness in his torso when rehabbing from the forearm fracture. Perhaps he had stiffness in his mid-upper spine, which could also lead to shoulder stress and dysfunction.
My point, which I’ve come to in my typically circuitous manner, is that if the cause of Kluber’s shoulder injury isn’t identified and addressed, he’s just going to have more injuries, regardless of how well recovered the teres major is. If the cause can be identified and addressed, he can be healthy throughout 2021.
The bad news is that although bio-mechanics is in fact, a science, it’s not an exact science. There are limitless combinations of factors involved in throwing a baseball that are in play here. The good news is that the Yankees have some very smart folks to deal with this sort of thing. Eric Cressey is as good as his reputation suggests, and Kluber by all accounts is a model subject (the man’s nickname is “Klu-bot” due to his serious nature, for crying out loud). So there’s reason for optimism, but there’s also a reason that the most accurate predictor of future injuries is the number of past injuries.
So let’s go with cautious optimism.
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