"A bone fragment from a bike accident 30 odd years ago was floating around," Manu explained.
"But also kept on growing and lodged itself just next to the ITB and caused inflammation and pain all the way to my glut (or my right bum cheek if you prefer)," he added.
In the post, Manu shared two close-up photos of his knee, as well as the bone fragment after it was removed.
"Anyway it's out and can get back to my boxing regime in 2 weeks!!! So relieved."
Just a few weeks ago, Manu let his fans know of the trouble his knee was causing him, where he shared a video of him at the gym while wearing a leg brace.
"I've been frustrated as I've had to hit the pause button on my boxing training regime because of a knee issue," he wrote.
"Getting fix soon but in the meantime I'm still able to work on the upper body," he said.
It comes after the chef was announced apart of the line-up for SAS this year, where he will be joining tennis champion Alicia Molik, Home and Away's Dan Ewing, NRL player Sam Burgess, TV presenter Erin Holland and ironman Jett Kenny.
Elite ex-Special Forces soldiers Ant Middleton, Mark “Billy” Billingham, Jason “Foxy” Fox, and Ollie Ollerton will all return for the season as the Directing Staff (DS).
The contestants will endure strenuous physical activity and military-inspired challenges throughout the season in order to put them to the ultimate test.