Bam Margera is currently laid up in a hospital bed ... and may have broken several bones ... after he fell down the stairs while "tackling" his neighbor ... TMZ has learned.

Margera says he was racing his neighbor up a set of stairs ... and promised the guy he could have one of Bam's skateboards if he won -- but, "Somehow I wound up tumbling down the stairs."
Bam explains, "I tackled my neighbor and fell down the stairs horsing around. I’m still in the hospital."
Bam says he's still unsure about the extent of his injuries -- but he may have broken his arm and several ribs.
Johnny Knoxville says he's been running through a gauntlet of emotions since his friend and "
Jackass" co-star
Ryan Dunn died last week ... ranging from mind-numbing sadness to anger directed at Ryan.

Knoxville went to his blog this weekend ... and explained why he froze up while speaking at Ryan Dunn's memorial service last week ... saying he tried his best, but "What came out were the mumblings of a man trying his best not to cry."
Knoxville writes, "Here is what I wished I could have told everyone then."
During the painfully honest blog, Johnny explains how much he loved Dunn -- he loved Dunn's "hair trigger laugh reflex ... Dunn was a great listener ... a great friend ... "as loyal as they come."
But midway through the tribute, Knoxville expresses his discontent with Dunn ... saying, "I'm becoming upset now because this isn't right, goddamnit. Ryan, I had to go wake up Madison and tell her you were gone. Do you know how hard that was?!! She loved you so much and I know you loved her, so why, buddy? Rocko will never get to know you like she did, nor will my daughter that is coming in October. I cry a lot about that."
Knoxville -- who refers to Dunn as his "brother" -- closed the post by saying, "I don't know what else to say right now, so I will close with I love you, Ryan. I have a lot of emotions swirling, but I want you to know I love you so very much."
Preston Lacy -- the guy who farted into the fart mask in "
Jackass 3D" -- was arrested earlier this month after cops discovered something else with potent fumes ... marijuana.

TMZ has learned ... Lacy was busted in Oklahoma on December 14 -- after cops say Lacy was in possession of a controlled substance (weed) and drug paraphernalia (rolling papers).
Lacy was charged with two misdemeanors -- and if convicted, he could spend up to two years in prison and face $2,000 in fines.
Attempts to reach Preston were unsuccessful.
We took your questions on everything -- including
Charlie
Sheen's car going over a cliff again, the
First Lady rolling through
West Hollywood and
The Situation being a diva on the set of "
Jersey Shore."

Plus:
Bam Margera's baseball bat beat down.
When
Bam Margera claimed that doctors had to literally staple his head back together after a woman allegedly cracked him with a bat a few days ago -- he wasn't kidding.

Bam was hanging poolside in L.A. yesterday with a few of his "
Jackass" buddies -- when he gave us a look into his busted up melon.
After the peep show, Bam told us he thinks his alleged assailant is in big trouble with the law -- check out the video to get his side of the story.
Bam Margera has a pretty ridiculous problem on his hands -- he says the concussion he suffered this past weekend screwed up his upcoming shoot for "
Jackass 3-D" ... because his stunt involved being hit in the head.

Bam tells TMZ he flew from West Chester, PA to Los Angeles yesterday so he and the boys could shoot the intro to the movie -- in which they're all supposed to take gnarly shots to the dome in 3-D slow motion.
Bam says his head-shot scene has to be rewritten because he suffered a concussion and internal bleeding on Saturday -- when he was allegedly attacked by a
bat-wielding 59-year-old woman.
As for Bam's replacement scene ... it's probably gonna hurt anyway.
Johnny Knoxville is putting his friend's genitals directly in harm's way -- so yeah, nothing new to see here.

If it looks like Knoxville is on a Ferris wheel trying to throw a basketball at a trampoline 60 ft. below so it hits fellow "
Jackass"
Chris Pontius in the family jewels ... well, then you're right. That's exactly what he's doing.
We're told Knoxville and his sidekick attempted the stunt -- filmed Friday in L.A. -- over 90 times ... without much success.
The two Jackasses have a history of getting testy.
When we broke the story yesterday -- that
Bam Margera was taken to the hospital after being
attacked with a bat -- we had no idea it was this bad.

The photos were taken immediately after the incident, as the "
Jackass" star was being loaded into an ambulance.
His condition is unknown.
UPDATE: We talked to Steve-O, who says Bam was holed up in the intensive care unit after the incident ... but has already been released from the hospital.
Steve-O also said, "I think he's gonna be okay."

TMZ has learned "
Jackass" star
Bam Margera has been hospitalized after being attacked by a bat-wielding woman.
Cops tell us ... it happened at 2 AM this morning, outside Bam's bar in West Chester, PA. There was some sort of fight, that ended when the woman allegedly hit Bam in the back of the head with a baseball bat.
The woman was arrested and charged with assault.
Bam was taken to the Chester County Hospital. His condition is unknown.
UPDATE: According to court documents, 59-year-old Elizabeth Ray faces the following five charges: Two counts of simple assault, two counts of recklessly endangering another person and one felony count of aggravated assault.
Steve-O isn't just happy because he's not going to jail -- after a judge dismissed a felony drug charge today for good behavior -- Steve-O's happy because now he gets to be sober just for himself. And it feels good.

The "Jackass" star stopped by the dreaded California DMV after appearing in court today with attorney
Barry Gerald Sands -- where he proved to a judge he's been 100% sober for 18 months since his arrest in 2008. The judge was so impressed he dismissed the felony drug charge for cocaine possession ... and even took Steve-O's arrest off his record.
But some things never change -- Steve-O tells TMZ he was at the DMV because he lost his wallet after getting naked and donning a wrestling singlet for an upcoming Jackass 3D flick.