In a bombshell announcement on Wednesday's episode of NBC's "Celebrity Circus," former "Brady Bunch" and "My Fair Brady" star Christopher Knight announced that he would be leaving the show due to a broken arm.

He announced that he had fallen in rehearsal the day before and did more damage to his already-injured arm. "This has been an incredible journey," Christopher said on Wednesday night's show, "and I really wish that I could continue the journey with you, but the doctors shut me down."

Speaking exclusively to ET about his exit, Christopher said, "I have to go start some new therapy tomorrow and re-heal it because it's now broken again, but it doesn't hurt, which is sort of troubling, you know, so I have to remember that it's broken so I don't use it."

And what does his wife, model Adrianne Curry, think about his early exit? "Adrianne is actually really sad for me," Christopher tells ET, "because she saw part of the act [I had planned for tonight] last week and was very much looking forward to seeing it tonight."

His final thoughts? "Big bummer, I mean it really is," Christopher says, "'Cause this is just a fun place. … I wish it didn't have to end [but] it does -- life is what happens when you're making other plans."

"Celebrity Circus" host Joey Fatone announced that Christopher would not have been sent home tonight, so one of the four remaining contestants (Jason "Wee Man" Acuna, Stacey Dash, Rachel Hunter and Antonio Sabato Jr.) had "gotten a second lease on life." Votes after Wednesday night's show will determine which three contestants will advance on to next week's finals.