JOEY Buttafuoco proved to be a knock-out for Fox’s “Celebrity Boxing” special.

“Celebrity Boxing 2” lagged behind the season finale of “West Wing” – but in the fight special’s final half hour, the ratings spiked as viewers apparently changed channels to watch Buttafuoco punch it out with pro wrestler Chyna (otherwise known as Joanie Laurer).

Early estimates indicate that ratings shot up 20 percent – from 10 million to 12 million – when Joey came on.

Wednesday night’s bout, also pitted ex-football player William “The Refrigerator” Perry against Manute Bol.