<qa>  What is the cause of pain in 10-27 of patients suffering from mechanical low back pain?This study will examine the effectiveness of sacroiliac joint SIJ diagnostic sensory blocks and radiofrequency ablation RFA under ultrasound guidance. The sacroiliac joint SIJ is estimated to be the source of pain in 10-27 of patients suffering from mechanical low back pain. When pain is refractory to conventional treatments such as activity modification, exercise, physical therapy, chiropractic, anti-inflammatory and analgesic medications and corticosteroid injections, radiofrequency ablation RFA is a treatment option in carefully selected individuals. 