Firstly, I would like to see that, while I am not a Doctor, I have the privilege of working alongside a Harvard-educated Physician every day, where I see numerous injuries ranging from MVA trauma, degenerative conditions, and most interestingly, major sports injuries. I thought it would definitely be a worthwhile task to go through a few things with you MCMers; to show how these injuries that happen every week in the NFL are not only impossible to accurately compare or predict, but are evidence of how the injury-prone tag thrown around recklessly by myriad fans, is nothing more than myth.
Physiology vs Circumstance
I suppose it is only natural to start with one of the major lightning rods for this conversation. Jake Locker has suffered two season-ending injuries in three years, along with a couple of others that have forced him to miss time. Let's focus first on his injury vs the Jets in week 4 of the 2013 season. Locker was hit by two players almost simultaneously, which bent his body back in an unnatural way, fracturing his right hip. After all was said and done, there was plenty of debate about whether Locker is simply injury prone or if this was a freak accident. I will say that, after all I have seen, both as a player on the football field, and in a medical office that sees current athletes and former Pro sports players every month, that it is more the latter.
There are literally hundreds of things to take into account when diagnosing the reason for any given injury. No injuries are the same, and I wholeheartedly believe that. The factors are beyond counting (Frame, conditioning, flexibility, neuromuscular processing speed, and prior injury history at specific locations such as cartilage loss, scar tissue, overuse, etc). In Locker's case during the Jets game, it's a matter of two forces twisting his body in an awkward manner, as well as with enough force to fracture the pelvic bone. To be honest, from a scientific standpoint, with that precise type of hit and in that exact situation, 9/10 NFL players would suffer an alike injury, the final 1 being the beneficiary of both luck and incredible physiological factors. This is simply a matter of physiology vs circumstance. Any given human body will suffer that injury if exerted upon by the same forces, but the degrees will vary due to bone density, frame size, weight, etc, etc, just like they affect recovery times from these injuries. This doesn't mean one player is more "prone" to injury than another. The fact that any given player, in this instance, Jake Locker, got hurt on this play isn't the result of him being "injury prone", simply the victim of circumstances beyond his control. In the NFL, this is going to happen.
In this league, made up of premier athletes who are maintained by possibly the world's finest fitness staff's and sports physicians, players participate in a game of luck with millions of dollars potentially at stake. I like to think of it as flipping a coin over and over, with a chance on injury with every hit. These players know this, and they've known it for a long time. With this in mind, you can look at it like the coin flip scenario, where you might get 3 heads in a row, maybe 7 tails in a row. Injuries in the NFL actually tend to be evenly distributed among active players statistically, but it is not a stretch to see how you can end up with a pool of players who constantly flip that coin and lose. That is where Locker has been thus far in his NFL career, and where players like Matthew Stafford have been in past years. Locker's not got a lingering injury in one location that he continues to aggravate, but he has been in the wrong place at the wrong time more often than some others. In the same vein, you don't hear too much about Matthew Stafford's injury-proneness anymore. So has he been cured of "injury prone-syndrome"? Has he simply lucked out with a string of un-injured performances? Or was he simply not injury prone in the first place? It's at this point you start to see the contra-indications of the moniker's existence.
Repeat Injuries and Concussions
Repeated injuries are a different ballgame. It is scientifically and medically understood that an injury to a certain limb/body location puts a human body an increased risk for re-injury at that same location more often than not. This is a result of cartilage loss, increase in scar tissue, even varying degrees of arthropathy (medical term for joint arthritis) and many more factors. That is not what we are considering in the injury-prone argument. I won't bore you with more on the subject, but it is generally accepted that this is the case from both sports medicine physicians as well as orthopaedic and neurosurgerons.
Likewise, concussions are a different story. Sustain one, and you are 4X-6X more likely to get a second, and a third, and so one. If anything, concussions are what you are looking at when really, honestly, accurately, talking about injury prone players. The source of repeated severe concussions are still up for debate, but it is understood that they result fairly often in pro football players to some degree; regardless of position (linemen generating concussions over repeated small blows vs WRs getting drilled in the head one too many times). Again, if you are looking at "injury prone" players, concussions and injuries to the same location are what to look at.
So what role does toughness play in this arena? We hear all the time about the "real men" from decades past who played through injuries because they were gritty and tough. Those same players were also going into games with undiagnosed injuries and aggravating them to an insane level, but that's a debate for another time. Let's rewind first to the role played by these elite athletes who play this physical game. Physical Therapists will be the first to tell you than bones can get stronger, and that leads me to the point that guys with physiological issues do not make it to the NFL. These athletes are worked out by the best of the best, and by the time they reach the NFL, they have already been playing this rough game for 8+ years. This process most certainly weeds out those unfit for the rigors of an NFL season. This line of thinking hearkens back to the days of McNair and George playing through the knocks in Tennessee to win games, including certain knocks that would force them to the sidelines in today's more careful approach to injuries, regardless of will to play or not.
A report surfaced earlier this year about Giant's running back, David Wilson. It was reported that he was thought to have spinal stenosis. Quick lesson on nerves: lumbar stenosis is a condition by which the lumbar spine has degenerated to a point that the foramina (the openings which the nerves travel through and eventually down to the legs to enervate muscle) have been compressed and are now pinching the nerves. These nerves then get inflamed. Think of a thumb in the door. I thought it was an interesting report in that the RB was then withheld from participating in games. With the intense amount of punishment going on in an NFL game, I would wager that there are very few players without some degree of lumbar/cervical spinal stenosis, or very least degenerative facet disease. The reaction to this injury shed a lot of light on how little analysts and fans alike know about spinal injuries. They treated it as if it was some exotic spinal condition. At it's least serious point, Stenosis results in mild intermittent limb pain with numbness. At worst, it is a requisite of spinal surgery, such as in the case of Tony Romo this past season.
Even just a few years of playing football will cause degenerative disease to some degree in the spine, that is accepted fact among professionals in the medical field. Basically, NFL players, and NHL players by comparison, are a radiologists worst nightmare. Not only did this news story shed some light on the lack of knowledge about spinal injuries, but also about the nature of injuries in the NFL in general.
I have seen the MRI images of former players at the High School, College, and NFL ranks, and I will tell you that the impact of playing football upon the muscular-skeletal system is intense and very real. Likewise, two similar reports will elicit different levels of pain from the individuals that present with them. Pain threshold play a part, but to assume that one player's bones/tolerance to pain, would allow him to avoid, say, the injury Locker sustained against the Jets, is simply a fallacy. Players today are no "less tough" than the iron-men football players of the past, but today's game is increasingly faster, with bigger players, bigger hits, and longer seasons. It is to be expected that injuries are also a rising concern, and that medical staffs are more attentive and cautious with the players. Remember, these guys are multi-million dollar investments for their respective teams, you have to believe they treat them as such.
There are two points here: (in my opinion) "injury prone" does not exist: it is simply physiology vs circumstance. Chances are very high that an NFL player will be injured at some point in his career, and suggestive that more than one is likely as well. While there is a pool of players who tend to fall to the wayside (and on the bench) due to injuries more often than their teammates, more often than not it is down to luck than it is due to being physiologically vulnerable to injury. Likewise, there are also lucky layers who fall to the other end of the spectrum and never sustain a notable injury, it happens. Sure, mindset and conscious caution while on the field also have a role to play (stepping out of bounds instead of delivering a blow for instance), it is simply reducing the volume of plays of which a player may be injured, not eliminating them. It's hard to believe, but it is what it is. Talking heads these days love to throw the injury prone moniker around, it is certainly a good debate starter, but just because a player sustained two non-related injuries in a short span means little in reality. But in the end of the day, it is just that: talk.
The other point is that no two injuries are the same. Put the human body to the test, much like a crash dummy in a car-testing tunnel, and run the results a hundred times, a thousand. You're results are going to end up more or less the same. Despite muscular differences, frame varieties, bone-density differences (which I can assure you are extremely minimal with NFL level athletes), etc, the human body has similar limits, especially when concerning flexibility of muscles and tendons, which is where a majority of sports injuries occur. It's simple anatomy, it's the way the human body is built. Push it beyond those limits and it will break.
Again, this is all simply the opinions of a non-doctor. Disregard it all you like, but please think again before you throw the "injury-prone" label on a player because he has been hurt more than once. The latter point of this debate will likely be more quickly agreed upon by you fine folks here at MCM, but since there is no realistic way to measure this kind of topic, it will continue to be debated as long as football players take to the gridiron.