What are common causes of lower right back pain that radiates down right leg to knee?

Lumbar DJD: Arthritic changes of the lower back (known as degenerative disc disease, stenosis, disc bulge, or foraminal stenosis) can all cause pain into the right leg from the back. Usually a l2/3 or l3/4 disc disease or facet disease cause these symptoms.

Disc herniation: Disc herniation below knee nerve pinched in spine above knee the list gets longer facet si jointmuscle spasm.