sounds like you need to stretch that part of your legs out some. You might try filling the bath tub up with hot water, then kneeling in it. The water being hot will loosen the muscles and tendons up and make it eaiser for you to stay in that posistion for a bit.
Eckards and walgrens carry a compond called Jointritis which works wonders on sore muscles and joints. a bit spendy but you might also try applying that before trying to sit sieza at all.