swollen knee

why am I having severe spasms that go from my buttocks to my knee and below the knee. it goes numb when this happens now my knee is swollen.  Dr. siad I have a bad lower 3 vertebres. the bottom one has piched my sciatic nerve bad. they do not want to do surgery, but put in a neurostimulator for my intense pain. Doen't it sound like there is something else going on here. when it spasms it does not tighten to the touch like a muscle and my leg and knee go numb and heavy.please help.