Can't speak to all yoga, and I specifically avoided the woo woo side of things, but it really did help as far as posture, flexibility, and various chronic joint pain.

The way it was explained to me was that various muscle groups were locked up trying to protect for example, my knee injury, so now my hips, back, shoulder, neck, etc where all out of whack.

The process involved working backward through the various muscles and joints, loosening them up so that we could work on the next group, until I could finally move and strengthen around the original injury.

I haven't gone for about eight years, but keep up with basic stretching and breathing excercises enough to maintain mobility.

In the end I'm going to require knee surgery to actually fix the root problem.