my back problems started with an attack of sciatica, i now have 2 discs that have crumbled away to nothing and 3 above them prolapsed causing nerve root compromise . specialist told me that my sciatic nerve runs through my piriformis muscle, which is egg shaped deep inside your buttock . Heres an exerscise that helped me ..........
get a golf ball , place it on a hard (dinning room ) chair sit on it with all you weight (on the affected side )and roll round with you buttock on it ,, he said youll know when you find the piriformis ,and he was bloody right it hurts like hell at first but it relaxes the muscle trapping the nerve.....well it did ease it for me for a while.