The funnyman was filming an MTV tribute to the late Evel Knievel when he tried to replicate the legendary stuntman's daring motorcycle backflip.
Knoxville had to be rushed to hospital after the incident earlier this month (Feb08), and will have to wear a colostomy bag for the next fortnight in order to let his injured penis heal.
Writing on his blog, he says, "Just got back from Oklahoma where I was shooting 'Mat Hoffman's tribute to Evel Knievel.' Had a ball, too, even though I almost lost my own balls in the process.
"Don't want to give too much away because the tribute airs February 23rd on MTV, but let's just say before letting (stunt trainer) Travis Pastrana teach me how to do a backflip on a motorcycle I should have had him teach me to ride one first. Heh-hehÂ… Bad for me, good for our viewing audience at home.
"Have to go now. Have to empty the piss (urine) bag on my leg that I have to wear for the next two weeks until my torn urethra heals. Ouch, and see you on the 23rd. By the way, lots of great stuff in the Evel Knievel tribute besides my trip to the hospital - lots!"