UPDATE 2-Former HealthSouth boss found liable for $2.9 bln

* Judge rules Richard Scrushy participated in fraud

* HealthSouth says "justice has been served" by ruling

* Company says unclear how much is collectible from ex-CEO

* HealthSouth shares up 3.7 percent (Recasts; adds plaintiff lawyer and company comment, details, byline)

By Melinda Dickinson

BIRMINGHAM, Ala., June 18 (Reuters) - Former HealthSouth Corp (HLS.N: Quote, Profile, Research) Chief Executive Richard Scrushy was ordered to pay $2.9 billion on Thursday after a judge said he was responsible for a massive accounting fraud that nearly brought down the hospital chain.

Scrushy, serving a seven-year prison term in a bribery case, was acquitted of criminal charges related to the HealthSouth fraud in 2005. But an Alabama judge ruled on Thursday in favor of investors in a civil lawsuit, finding that Scrushy played a key role in the accounting manipulation.

"Scrushy knew of and actively participated in fraud," state court Judge Allwin Horn said in a written ruling.

Last month, Scrushy came to court in leg shackles to testify in the case, which the judge heard without a jury. The former CEO said he had no knowledge of financial problems at HealthSouth, reiterating the argument used at his 2005 criminal trial, where he contended he was duped by subordinates.