Pain in back and leg

Patient: I had a sudden onset back pain. Lower back just above my butt and across the lower back. I also found that I have a pain in my lower left leg. There is no pain in the thigh. The pain in the left leg is on the side under the knee.It is difficult to stand.I have read the response on sciatica but I am not sure if that is what I may be suffering from. I tried using Arcoxia 120 mg but the pain is persistent.