Yes absolutely. Flexibility and strength start with the muscles, makes the tendons and ligaments stronger and also affects the density of your bones. This should be pure and simple proof beyond any doubt, about the importance of the flexibility, strength, alignment and well-being of every part of the body and how it affects other parts from performing well.
Improving the actual quality of your muscles and connective tissue by being active, doing a few minutes a day of general stretches and, if possible, strength development exercises, is the other aspect of this postural re-education equation. Long-term correction of your posture will only happen when all aspects are understood and addressed. This will be done in stages, and the pace will be determined by you.