Your low back pain
may be due to muscular spasm of there may be any disc abnormality. You should have an xray and then MRI for lumbosacral spine that will tell you about your disease.
Knee main is due to inflammatory joint disease
of pain from the lumbosacral region. You should have complete workup that include MRI for knee joint, Serum Uric Acid levels, and Rh factor
and CRP levels.
I hope I am sucessful in solving your query If u have further you can ask me
Get well soon
Dr. Azhar Sattar