Earlier in the week Sean Sherk announced that he was calling it quits on his decorated career, and now the former UFC lightweight champ has provided more details as to why he’s hanging up the gloves.

It’s been known for some time that Sherk hadn’t fought since September, 2010 (when he beat Evan Dunham by split decision) due to injuries, but the 40 year-old recently relayed to MMA Fighting.com just how serious they were.

“Now that I’m retiring I can tell the truth,” Sherk said. “I know it’s always been one of the top questions. Obviously I couldn’t say anything because otherwise opponents would pinpoint that stuff, but I had MRIs done [ahead of the Penn fight] and found out that both of my hips were torn and that I was going to need surgery. The doctor basically told me at that point in time, ‘if you have surgery on this you’ll never be 100 percent again – you’ll lose your mobility, you’ll lose your quick twitch and some of the explosion, and you’ll lose some of the agility.’

“And to me it just wasn’t worth it, so I said, you know what, I’ll just deal with the pain. I said, I’ll just deal with this as long as I can. And that’s what I did. Gradually over the years my hips got worse and worse and worse. About two weeks ago I was told I needed hip replacement surgery. So that was the deciding factor right there. I went from needing surgery to fix torn labrums to needing total replacement.”

Sherk finished his career with an awe inspiring record of 36-4-1, and his only losses came against former or current champs in Georges St. Pierre, Matt Hughes, BJ Penn and Frankie Edgar.

The highlight of Sherk’s career? Understandably, “The Muscle Sherk” said defeating Kenny Florian to win the lightweight belt in 2006.