Best way to get knots out of hair?

After being sick and primarily bed ridden for months, my hair is full of knots. The last time I tried to get the knots out, it was pretty painful and I wound up cutting them out with a scissors.

If necessary, I will just cut the knots out, then go to a hair salon and get my hair cut short in layers. That might be my answer. But...does anyone here have any ideas or techniques for dealing with extreme hair knots?