Question: why does it hurt when i lay down on my back?
Answer: Nocturnal back pain is also a symptom of spinal bone infection (osteomyelitis) and ankylosing spondylitis (AS), a condition that can cause the spine to fuse in a fixed, immobile position. Other "red flags" include: Back pain that spreads down one or both legs. Weakness, numbness, or tingling in legs.