I use the tennis ball method of massaging the SI joint area. For
example, go to
http://kelziebeebe.blogspot.ca/2011/06/self-massage-with-balls.html
and search for the phrase "Butt and Back of the Thigh" without
quotes. I find that the tennis ball gets soft very quickly, and I
don't like the variation of hardness as the tennis ball ages and gets
replaced. Is there a hard-ball version of the tennis ball for
physiotherapy purposes? It should be textured on the surface so that
it doesn't slip as one rolls around on it. The closest I found was a
hard BASEBALL, but only texturing is the threaded seams.
From surfing the web, I ran across the idea of a lacrosse ball (http://
en.wikipedia.org/wiki/Lacrosse_ball) but it might be a bit small (or
my cheeks are too pudgy).
Thanks.