Suggest Treatment For Knee Pain

I GOT A NARROWED DISC SPACE BETWEEN L4 AND L5 AND IT IS HURTING ME TOO MUCH CAUSING PAIN EVERY TIME .I CAN BEND ONLY BY BENDING MY KNEES.I HAVE TRIES PHISIOTHERAPY.I CANNOT SIT FOR MORE THAN 30 MIN AND CANNOT EVEN STAND AT ONE IPOSITION FOR TOO LONG I CAN WALK QUITE FAST . CAN YOU HELP ME IN THIS DESPERATE SITUATION WHERE I CANNOT HAVE A NORMAL LIFE I AM 49 YEARS 176CM AND ABOUT 82 KG IN WEIGHT.TABLETS LIKE PARACETAMOL DICLOFENAC AND CODEINE ARE ALSO NOT WORKING