My Wife Has A Knot-like Bulge In Her Lower Left

My wife has a knot-like bulge in her lower left back. That side appears swollen. She cannot put weight on her left leg and foot without excruciating pain. The ER diagnosed back strain and prescribed pain pills. She has not improved, the pain radiates from left back to front. She can lay on her left side only without pain. She has scoliosis that developed in adulthood. Could this pain be from something other than spinal disc or other skeletal problem?