Johnny Knoxville nearly put his penis "out of commission".

The 50-year-old star of the upcoming Jackass Forever, the latest instalment in the daredevil franchise, recalled how he once injured his “gym dog” in 2007 while doing a stunt which saw him trying to flip a motorcycle, and left him with a catheter for more than three years.

He told Variety: “I broke my gym dog a number of years ago. That’s been well documented. So much has been said about so little.

“The doctor said a couple centimetres down and it would’ve been out of commission.”

However, the Bad Grandpa star joked the birth of his two kids - son, Rocko, 12 and a daughter Arlo, 10, with his wife film director Naomi Nelson - proves everything is in "working order" now.

Johnny quipped: “But I’ve had two children since then, so it’s in great working order. That’s too much information.”

Over the years, Johnny who also has daughter Madison, 25, with ex-wife Melanie Cates has experienced multiple other injuries while filming on Jackass, both the 2000 MTV series and the subsequent movie spin-offs. The damage list includes a broken wrist, broken rib, concussion and a brain haemorrhage.

Johnny, whose only stunt in Jackass Forever is featured in the trailer where a bull knocks him over, revealed his family don't approve of his extreme behaviour.

He said: “My family doesn’t like me doing this type of thing. This is the most wicked bull hit I’ve ever taken.”

Johnny has opted to take a back seat this time around and let the next generation take over, such as Zach Holmes, Rachel Wolfson and Eric Manaka.

He explained: “Those were big, and could end as badly or worse. I’ve done enough. I don’t have anything to prove. I have kids to raise. That’s the most important thing.”

The original show also featured the likes of skateboarder Bam Margera, Steve-O and many others, and Johnny admitted it was "heartbreaking" working on a film without the late Ryan Dunn, who died aged 34 in 2011.

He added: "It was a brutal loss for everyone and something that sticks with me and all of us to this day. My kids don’t know Ryan, and it breaks my heart.”

Meanwhile, Bam also doesn't feature due to personal issues, as Johnny said: "We all love Bam. He's our brother, you know? You just hope that he takes it upon himself to get the help that he needs, because we all care about him a lot."  

Jackass Forever opens in Singapore cinemas on Feb 3.