On 12-21-04, injured filled out an accident report stating that as he attempted to pick up rub rail on M4 miner he felt pain in lower back. Injured continued working. On 12-28-04 injured called & said that he went to the ER on 12-24-04 & to the chiropractor 2 times since then. Injured returned to work on his next regular scheduled shift. Didn't become reportable till 12-24-04.