The 27-year-old singer was forced to cancel most of her North American dates for the Born This Way Ball tour in order to undergo surgery to repair her hip last year, reported Contactmusic.
"My heart breaks from the people I have trusted and loved who I've worked so closely with, who have used me, lied to me, worked me into the ground for the personal gain," Gaga posted to fans on a website.
"When I woke up in the hospital after my surgery there were many people that were not there. My health did not matter. I did not matter unless I could perform. This is a very hard lesson," she added.