Does Bad Posture Cause Injury?
Sounds like a dumb question, right? But I should say that the evidence that bad posture causes injury is scant, yet at the same time I think doctors, physios, and basically everyone with any common sense realises that it is a big factor, they just don't know the specifics. The lack of evidence is due to the difficulty in isolating posture as a cause or even a contributory factor amid the vast array of other possible causes for an injury, either chronic (developing slowly over months or years) or acute (occurs suddenly, like a sprained ankle).
The commonsense theory goes that if your joints aren't aligned well (for example, knees are aligned with your feet from front on), and you aren't stacked correctly in your posture (i.e. head over shoulders, shoulders over hips, hips over knees, and knees over ankles) you are placing increased force on joints when standing, sitting, or moving. Over the years this daily force going through your joints - that is poorly absorbed - causes chronic pain and injury. As your posture degenerates, you also have more trouble maintaining core stability, making it difficult to make smooth, well-balanced movements. Makes sense to me. What is often ignored, though, is the effect bad posture can have on acute injuries.
Women Vs Men
There is actually some relevant evidence we can look at, we already know that women are much more likely than men to get lower limb injuries during sport. Very few people know of this fact, and I actually think it irresponsible given women are now much more involved in sports like football, basketball, and AFL, all great sports for knee and ankle injuries. I'm not saying girls shouldn't play these sports, but some knowledge of their extra vulnerability to injury playing them could help coaches train them better and possibly avoid nasty injuries like ACL tears, which are worryingly common.
Why then are women and girls more likely to get injuries in their knees and ankles? There are many differences between men and women, but there are some key differences. One is the fact women are designed to give birth. Having a body that enables a baby to pass through the birth canal means that the hips have to be proportionally wider (men actually tend to have wider hips because of their size, but it is hip to waist ratio that is important) and this creates an angle that is sub-optimal when it comes to human athletic activity. This angle of the femur from the hips to the knee does not spread the force of impact as evenly as the much straighter angle of the male femur. This makes it more likely that turning sharply or landing hard is going to tear ligaments, tendons, or cartilage.
Scientists can look at the incidence of knee and ankle injury between populations of men and women playing a particular sport or doing an activity and see who gets injured the most. Unfortunately though, we can't see anything other than the injury itself; the internal stresses and signs that could precede an injury are basically impossible to test.
There are a few possible significant factors also that make nailing-down a cause extremely problematic, like hormonal difference and core stability. Core stability is heavily influenced by posture, as without good posture correct activation of the TVA (transverse abdominus), which stabilises your hips and spine, is impossible. However, I'm not seeing this link between posture and core stability anywhere in the literature.
The evidence shows that once girls have hit puberty they are 2-8 times more likely to suffer knee or ankle injury (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4805849/).
Differences in anatomy and core activation are important then, very important. This is why every expert in the human body worth their salt knows that correcting posture is a good thing. The problem is that up until very recently, no one had any effective ideas about how to do it. With no results and no reliable mechanism or strategy for improving posture, comparing populations was impossible, and seeing as posture worsens with age, comparing a young man with an old man and deriving that it is their posture that injures one more than the other is obviously a non-starter. Even people of the same age with clearly different posture are not easily testable because people's posture differs and changes with time and they do different activities on a day to day basis. You'd have to study people for decades and control for an almost unlimited number of variables, and this obviously is tricky to say the least.
When I tell people that they can improve their posture, I am often met with disbelief, but why is it so hard to believe? After all, if activities like working on a computer or driving can change your posture in a negative way, why can't you do activities that change it in a positive way?
Only fairly recent discoveries in the importance of fascia have shed a light on how posture changes in the first place, let alone how to make positive changes. https://www.thefreetrainer.org/post/exactly-how-your-posture-worsens-with-age
Personal Trainers and Movement Coaches
Back in ancient Greece - where the idea and the name of the 'gym' was born - people had trainers too. Unlike today, these trainers were also often highly revered physicians that were encouraged to train people and exercise themselves to understand the human body better. A PT in ancient Greece was a very qualified and respected person (by ancient Greek standards). Unfortunately, these days a PT is often seen as someone to push you to lose weight, build a six-pack, or just dole-out a catalogue of exercises to keep you fresh and motivated. Although many of these are noble causes, PTs are not seen as experts in any meaningful sense and personal trainers are generally young and inexperienced, as the average length of time in the industry is less than 18 months. I see PTs as having a very important role and should be much more highly qualified and therefore respected, it could and should be a very highly specialised and important job.
If you have a problem you should go to someone who knows how to fix it; those who know how to fix specific problems are generally those that spend their time focussing on it. If you are sick you see a doctor, not just because of the qualifications, but because they see sick people every day. If you are injured, you see a doctor or a physio because they treat injured people every day. But who should you see to improve your posture and movement? How about someone that watches people move and lift weights every day? This is particularly relevant to trainers as identifying, especially movement dysfunctions, often requires higher intensity movements. The flaws in people's biomechanics show themselves much more clearly doing high intensity movements like sprinting or lifting weights.
In the last few years, we have seen the evolution of movement coaches, a different kind of PT, that are designed to improve the way people move. Many of them have some crazy ideas because, in the gap that solid evidence about how to change posture and improve movement vacates, lies a lot of dumb theories. It was inevitable, however, that those looking at people move, day-in, day-out would come up with some answers that make sense, and things are starting to happen (Look to functionalpatterns.com for the best in the field, in my opinion).
Resistance to Change
What we are discovering is that a whole load of activities can make posture worse and to improve posture requires a lot of accuracy and practice. Selling this reality to people is not easy because it involves 2 things; 1) Giving-up (or at least reducing) some much loved activities; and 2) Diligently practicing something you aren't very good at and that is not supremely entertaining and even painful. When you add the fact that science is yet to have a definitive say on this question, generally the only people that will try these things on faith and reason alone are those that have gone through injury problems, are not willing to accept chronic pain, and have found no answers elsewhere. As a practitioner, these are also just the kind of people that I find it the hardest to teach and make progress with because they are so restricted in their movements.
Results with training posture and movement come slowly, they don't make you attractive to the opposite sex, and they require a lot of time and practice to bring about. Is it any wonder people aren't knocking down my door, especially in today's busy world? However, the answers to the problems of life are always where you least want to look, or else you'd have found them already.
The hard pill to swallow is that as you age all of the things you enjoy doing physically will be taken from you, one-by-one, unless you do something about it. If you are a very physical person, it may only take not being able to play a sport or run to drive you to change things, but understand that even if you simply enjoy going out to walk the dog or sitting down and reading, these simple activities will be taken away from you with time also (at least doing them pain-free). It doesn't have to be this way; personally I'd rather enjoy my life right up to the point I finally snuff it, rather than suffer through the later half of it with chronic pain and injury.
Back to Acute Injury
What are the chances then with joints forced out of alignment with age, which not only destabilize the joints but also make it hard to gain core stability, that the next time you land awkwardly, step on an uneven surface, or have a minor slip, you can balance yourself in time or adjust adequately to avoid a sudden injury?
But what caused this injury? The fall? The slip? The rock? The mud? In the doctors report, it will be the environment's fault and some bad luck, but who knows what would have happened if you'd had better control of your body and your joints were stacked properly. That little dose of ill-fortune is right around the corner, why rely solely on lady luck? How about stacking the deck in your favour? There are no guarantees, you can get injured with or without good posture and movement, but your best bet is something you instinctively know needs improving when you look in the mirror. Everyone knows it, and now we are beginning to understand how we can achieve it.