You can't stretch connective tissue that covers bone, well at least not in the way we think about stretching traditionally.
Most people when they think of the word "stretch", they think lengthening, creating more distance between two points. Like stretching a rubber band for instance. The same concept applies when we think about stretching our muscles; we try to create a greater distance between the two attachement points of the muscle. We feel tight, restricted (or whatever term you like to use) and so we think we need to stretch our muscles. In reality our muscle don't really lose their elastic (stretch) properties, what happens is that the connective tissue that surrounds the muscle fibres and bone and pretty much everything else in the body becomes glued up, stuck, unable to glide over the top of each other.
So instead of stretching our muscles, perhaps we need to look at un-gluing, un-sticking, getting the glide back.
Here's one technique that I've found really useful...... And all you need is a tennis ball!!