How high are your sofa arms? Anyway lie on your back at the side of your sofa and rest the bend of your knees on the sofa arm, get your bum as close as comfortable, then point your toes down. Your back should be off the floor by now and the gravity stretching it, it's nice and the trap might fix. Otherwise as a last resort I get my husband and kids to pull on my legs while I hold tightly to a secure surface. Desperate I know but they don't do traction anymore. Or I get my 6 yearold to walk on my back, it's great fun, really helps (for me anyway).