My surg. told me fairly early after surgery...don't recall...maybe 6 weeks or so....that I'd better "massage the heck out of" my neck. He meant breaking up the scar tissue. Scar tissue doesn't stretch, so this sort of massage needs to be done as soon as possible after surgery, to keep it broken up as it heals. My neck feels nearly normal, exc., of course, for the numbness of the skin flap which I honestly do not even feel.
Of course, I did not have rad., but the principle is the same....massage as soon as the dr. will let you, and move the skin around as much as you can to keep it from adhering to the underlying tissues.
I also did plenty of neck stretches and jaw stretches....still do them. .and range of motion exercises.
Maybe this thread will keep others from having this problem. Nobody really told me why I needed to massage......The doctors don't realize that we aren't born knowing this stuff.
This is another area where, if you don't know about it, you'll wait too long.