Dealing with Pain and Poor Posture
If you are going to try and fix any problems of pain yourself, I'd suggest that part of that process includes learning to feel and control your body
The feeling/sensing part is how you try to diagnose what is causing the problem. The controlling part is what you do to fix the problem.
Learning to feel and control your body is a very long process. And you may find yourself going in circles, till you figure out what you need to do in order to go deeper. But if you deal with problems in other areas, the same process applies. In either case, the better you understand what you are dealing with, the easier it is to fix problems, (or redefine problems so that they are fixable.)
If posture (or a lack of good posture) is the problem, the same thing applies. Practice feeling your body and controlling it so that you can then find good posture, supportive posture, with minimum effort.
Pain is a pretty useful signal. In general, it's your brain telling you something isn't right.
With joint pain, it helps to understand that your muscles directly affect your joints. Muscle tension affects joint capsule tension which in turn helps to keep your joints lubricated and your joint capsules intact.
Joint pain may be your brain telling you that a particular joint is in danger. And so a way to deal with joint pain is to experiment with muscle control so that you can find the muscle activation that alleviates your pain.
Muscle pain can be a signal that you are overworking the muscle in question. Why that muscle is overworked (or tight) may relate to poor posture. It could also relate to your brain protecting a joint. One muscle isn't working properly, so your brain uses another muscle to substitute, and over the course of time that muscle gets overworked.
Here again the solution can involve playing with muscle control to try and fix the problem.
Note that muscle control is a dual process. It involves deliberately activating or relaxing muscles. But is also involves feeling them when they activate. Muscle control is thus a means of feeling your body as well as controlling it.
A similiar process can be used to deal with poor posture. Instead of dealing with a pain signal, poor posture is something you can see and in some cases feel. It can become obvious when doing particular poses or actions. Or it can become obvious when you look at yourself in a mirror.
How do you define poor posture?
Usually it is something that we can see, or that other people can see. But that's not really that helpful except as a starting point, a recognition that you have a problem.
One way to look at posture is that the process of creating good posture is actually about setting your body up so that you can feel it. Good posture then becomes the act of adjusting your body, by feel, so that it feels good (or "comfortable") and or so that it helps you do what you are trying to do.
If you are just standing or sitting around good posture can simply mean adjusting how the parts of your body relate so that effort in holding your spine upright is minimized.
This is actually more than just "stacking your bones". Instead it's using muscle activation and connective tissue tension to control how your bones relate.
The nice thing about approaching posture in this way is that it allows you to actually feel your body. The muscle activation, the connective tissue tension, both of these are things that give you "feel" or "proprioception".
It's a lot like in the old days where setting up a tent involved adjusting tension to the guy wires so that the tent was nice and neat and would stay upright even with a wind blowing. Adjusting the guy wires you can feel when they are tight and you can visually check when tension is balanced so that the tent is nice and neat.
With posture, connective tissue tension is something that you can feel and adjust. And likewise, muscle activation sensation is also something that you can adjust for (by feel). The result can be a posture that is nice and upright or one that helps make it easier for your to accomplish whatever it is that you are doing.
With good posture, you use muscles and connective tension to control how the parts of your body relate. But in addition, you use the posture of, say, your torso to help drive or support the action of your arms and legs.