I'm so sorry for the loss of your friend. It happens more and more as we get older.

Have you tried lying on the floor with your knees over a stool or low chair? Thighs have to be straight up in the air, not slanted. A doctor once told me to do that for my back because it straightens and supports the lower back. Never helped me, but maybe you will have better luck. Gives the kitties a bit of novelty at least.