Actually you can just bend the foot to the appropriate angle in the first frame of the animation (usually around 45 degrees I think). Then remove all keyframes for the foot bend for the rest of the animation so it stays at that angle. (Also remember to adjust the figures position relative to the ground if that is important for your animation). It works pretty good, and I have used this trick. If you think about it, a woman doesn't really bend her foot much while in high heels, hence the reason why it is such an easy fix.