Take a cutting or cut off a small portion & pot in fresh potting mix.

Because it's such a spreader it's crowded itself out, so you either repot like previously suggested
or
*cut a checkerboard pattern into it with a sharp knife.
*pull out by hand the twiggy dead stuff.
*fill in empty spaces w/compost

& the mint will vigorously spread back into those spaces this growing season.

Thanks for the advice.
Will certainly thin it out...planning to plant them into the slope with some good soil...and I don't care if it spreads there....and can enjoy a lot of mint that way...

You probably just need to divide your mint into smaller plants and if don't want that many, give it away. Plants always make great gifts to fellow gardeners! The mint in my yard is not as vigorous yet as in years past. I think the long cold wet winter and spring just set it back a bit. By now mine its usually 2 feet tall at this time and this year it has barely reached a 8 inches. I also transplanted this into the ground a few years ago from a small pot. It hasn't gone completely crazy yet but it is spreading. Just a nice low shrub look. Also, each winter I cut it all the way the the ground. Even took some mint out of planters last year and still haven't planted it. It just sits in a plastic bag open with roots exposed all winter and its thriving.