You may be suffering from Sciatic pain
. Because of your lower back problem all other problems have come. Sciatic is the longest nerve starting from lower back moving along with your thigh knee up to the ankle.
Identify the dipping portion on the back of your knee folding. Press this dip with both middle fingers and hold your knee with your thumbs for support. Swing 20 times morning and evenings. This will relieve your problem. In case it continues consult a Acupuncture/Acupressure Dr. In your place