Conor McGregor says he was already injured before suffering a broken leg in the fight with Dustin Poirier at UFC 264.
The Irishman, 33, said he had "multiple stress fractures" to his shinbone above the ankle when he was beaten by American Poirier in Las Vegas.
McGregor said on Instagram there had been talks about whether the fight would take place.
He added: "I have trouble with the ankle anyway."
Television replays of the bout showed McGregor rolling his ankle as he stepped backwards, seconds before the end of the first round, which resulted in a break to the lower tibia in his left shin.
The fight was stopped by doctors and former interim lightweight champion Poirier, 32, was handed a second straight win in their trilogy of bouts.
Filming himself on a motorised scooter while recovering from surgery, McGregor said UFC officials were aware of the issue prior to him entering the octagon last weekend.
"Everyone keeps asking me at what point did the leg break?" he said. "Ask [UFC president] Dana White, ask the UFC, ask Dr [Jeffrey] Davidson, the head doctor of the UFC.
"They knew... I had stress fractures on my leg going into that cage.
"There was debate about pulling the thing out because I was sparring with no shin pads and I kicked the knee a few times, so I had multiple stress fractures in the shin bone above the ankle."
McGregor added training sessions for the lightweight encounter were difficult as he kept twisting his ankle.
"I even did a lot of training sessions when the ankle was sore, I still wouldn't stop training," he said. "I used to train on my back and that's how I developed those ground and pound shots from the back.
"It was a skill I developed because of the damaged leg and I had to adjust my training."
McGregor, a former two-weight world champion, revealed in the video he now has a titanium rod inserted in his leg, from his knee down to his ankle.
Once he has regained balance and strength, McGregor joked he would have an "unbreakable" titanium leg, like "Arnold Schwarzenegger in Terminator 2".