There is something very sad that is happening into our culture, as people age, they become so rigid and stiff that they could barely function. It becomes nearly impossible to bend down and tie your own shoe laces. So people of a certain age stop wearing shoe laces.
That shouldn't suppose to happen, you should at least be mobile enough to have basic functionality, like be able to dress yourself, for the entire duration of your life.
An inflexible joint is not necessarily caused, by the tight muscles around it. Your body has to maintain equilibrium, if any weight moves forward or backwards, your center of gravity is going to change.
So in order to maintain equilibrium your body is going to overcompensate by changing the position of other joints in order to bring that weight at the centre.
This is why you can see someone with 30 degrees scoliosis, and from the outside doesn't look unusual. Because his thoracic spine is bent at 30 degrees on one side, and his lombar spine is bent at 30 degrees to the other side.
The same thing happens from the side, if you have a reversed curve in the neck, you are going to overcompensate by overarching your lower back.
If you have tight hips, which is incredibly common, you can stretch your hips as much as you want, those hips are going to remain tight because the lower back is overcompensating for the misaligned neck which makes the pelvis tilt forward.
Which is why you have tight hips. Your tight hips are caused by the neck and can be solved only by fixing the neck.
This joint equilibrium overcompensation principle is why you don't need more than one exercise to reshape the entire body.
You always start with the highest mechanical compromise, fixing that joint is going to eliminate the need for your body to overcompensate, and the joints underneath are going to self correct.
All stretches are full body stretches, there are no shoulder, hip, neck, finger etc. stretches. Everything is connected and influences everything else.
When you stretch your neck, you are stretching your entire body. Parts that you are not working with will change and even get sore.
Aligned joints are mobile joints, misaligned joints are stiff and immobile. Flexibility is just a side effect of having a well aligned body.
Think of it like this, if your pelvis is tilted forward at 20 degrees when you are in a neutral position. Your hip joints are 20% closed at neutral. So if you try to bend from the hips you are going to bend less by 20%.
Restoring propper alignment, restores propper mobility.