lower back pain

The lower aspect of my boyfreinds back gives him a lot of pain. His muscles at the side of his erector spinae feel like they are in constant spasm/contraction, they are rock solid and no amount of massage/palpatation or stretching seems to help them. He said it feels like a muscle pain rather than on a bone and that deep massage feels nice on them. I don’t know what muscles they are, (sacrospinalis?)Please are you able from this breif description to tell me which muscles they sound like, what’s wrong with them and how can they be treated. He didn’t do anything to his back to get this trouble, he’s just developed it. He is now 22 and it’s not getting any better. Any help would be most appreciated. Thank you.