Ihave had a hip replacement one year ago I have lower back trouble with sciatica getting terrible pains inbuttocks and down left leg also pain in my knees.? Would my other hip need replaced

Not related. Hip arthritis does not directly cause sciatica. If your left hip has been hurting and it has been causing you to limp, then your hip may indirectly affect your back but increasing the lateral strain on your back due to the limp. If your left hip does not hurt, you are unlikely to need a hip replacement. Go get an xray.
Sciatica. You have the cause of your sciatica investigated. Probably due to a lower back problem. You will probably will not need another hip replacement.
Given Your Pain. I would suggest seeing a pain/spine specialist to evaluate you further to evaluate what level and what can be done to treat you. There are interventional treatments besides medications and surgeries that might reduce or eliminate the pain altogether. Hip replacement for the other leg might not be necessary. Generally its not a treatment for sciatica.