I Have Had A Number F Spinal Surgeries Over The

I have had a number f Spinal surgeries over the past 3 years:
co-flex stabilizers put in... Three months later these taken out because pain persisted.
4 regular one inserted. Lower spine fused. Months later, more pain. Dr. found hole in femur
plugged it up - also inserted rod up femur of rt. leg. Because of no exercise, the muscles in both legs
have atrophied.... I'm trying to build up my leg muscles. If I sit too long; stand too long.... leg seems to go numb; tingling in toes... Is this all from the spine or from the terribly weak knees ?