Tool frontman Maynard James Keenan had hip surgery this week – but kept it secret until he was certain it had been successful.

He says the treatment was required after a lifetime of wear and tear built up.

And now that he’s on the mend, he’s looking forward to attaining a brown belt in Brazilian jiu-jitsu, after recently receiving his purple belt.

Keenan says via Facebook: “Didn’t want to freak anyone out – wanted to wait until out of the woods.

“Years of foot stomping left me with no cushion in my right hip. Full replacement yesterday. Walking today.”

He adds: “12 weeks, back on the mat to work towards that brown belt.”

Tool are continuing work on their long-awaited fifth album. Guitarist Adam Jones said in March that the process would speed up after the band concluded an eight-year legal battle.

Keenan said earlier: “I’m as anxious to get this album completed as everyone else. But as history will show, you can’t rush these gents.” He recently reported that he’d finished an album with Puscifer, but didn’t offer any release information.