What would cause chronic pain in lower back and r leg? (2.5 years: sharp pain, tingling, numbness, weakness, purple color in r leg at times, cramping in calf, severe flare ups at times, tender touch)

Consider CRPS: Such pain may be caused by a disorder called complex regional pain syndrome (CRPS). CRPS may start with a relatively trivial injury, but the pain persists far longer than usual. It may be associated with swelling and/or color changes of the limb. Unusual sweating or changes in the nails may occur. CRPS is usually diagnosed and treated by pain specialists, especially pain anesthesiologists.

Exam and XRays: Problems in your lumbar spine could explain the pain, tingling, numbness and weakness, but not the purple color , cramps and tenderness of your calf. You need to see your physician for an examination, appropriate XRays and other tests to clarify the problem.