Hello, I am experiencing issues with my back and left knee. When I sit for a while and stand up I cannot walk right away I have to stand and stretch for a while before I can walk. Sometimes I get a throbbing sensation behind my knee and have to keep my leg bent. I cannot sit on a flat surface such as the floor or even the bed with my feet straight they have to be bent. I cannot kneel down at all once my toes press on the floor I get a throbbing sensation shooting up my body. I think there is something wrong with my nerve endings.