As time goes on and I become older, I've started to noticed a lot more aches and pains. It seems like all of the muscles in my lower body are constantly tight. My hamstrings feel like wire, when I sit on my heels, my quads feel really tight and while I used to stay relatively injury-free, I've been struggling to stay healthy over the past year.
Back in the day, people would just treat an injury. If your knee was hurt, you'd be told to strengthen your quads (especially your VMO, which you actually can't individually train). If your achilles was injured, you focused on the calves. Research now shows that the muscles in the lower body all work together. Weak/underactive glutes can result in achilles tendonitis. A tight psoas can result in a gimpy knee. When people thought they were treating the "disease" they were actually only treating a symptom.
I believe a lot of my aches are due to weak glutes and tight muscles around my hips. The following is a good link that discusses pelvic alignment and shows some good stretches to loosen things up and get all of your muscles working together more efficiently.