Howe was knocked out in a dramatic opening before the Hawks pulled away with a dominant seven-goal second quarter to set up their crucial 17.8 (110) to 6.10 (46) victory at the MCG on Thursday night.
It ensures Hawthorn (14-7) will retain a spot in the top eight for at least another week, ahead of clashes with Melbourne and the third-placed Brisbane Lions to complete the home-and-away season.
Collingwood (15-6), who were ladder leaders for 11 consecutive weeks, have now lost four of their last five outings and will be without Howe for at least one more match.
The experienced defender's return from a hamstring injury lasted less than two minutes when he collided with Newcombe as the pair chased a loose ball.
Howe got to the bouncing ball a fraction of a second earlier than his opponent and took possession before he was cannoned into by Newcombe, who looked like he was attempting to tackle.
The pair appeared to clash heads and Howe also hit his head on the turf when he landed.
The 35-year-old was knocked out and taken off on a stretcher, but was alert and walking around the changeroom before being taken to hospital for precautionary scans.
Collingwood coach Craig McRae admitted the injury "rocked" his players but did not want to make excuses for their worst performance of the season so far.
The fact it came in club great Steele Sidebottom's 350th game rubbed further salt in the wounds.
"I apologise to our Magpie Army. That's a disappointing performance, you can't sugar-coat that," McRae said.
"We owe Steele Sidebottom way more than that too. He's a legend of the footy club.
"We're hurting. That one really hurt.
"It was just a lack of system and then a lack of fight and lack of effort, sometimes at the same time, which leaves us really vulnerable."
Hawks midfielder Newcombe (28 disposals, seven clearances) was also groggy after the collision with Howe but passed a concussion test and returned to be one of his side's most important players.
"It's just part of the game, both committed," Newcombe told the Seven Network at halftime.
Hawthorn's talls were damaging in Howe's absence as outstanding ruckman Lloyd Meek (three goals), Jack Gunston (four) and Mabior Chol (three) all hit the scoreboard.
"My thoughts straight away go to Jeremy Howe. He would've been a big part of their plan for that," Hawks coach Sam Mitchell said.
"When you have big moments like that early in games they can rock you as a club.
"That was obviously a significant moment and he would've been important for them."
After the dramatic start, Nick Watson's two early goals gave Hawthorn a narrow quarter-time advantage.
They took complete control in a scintillating second term, piling on 7.0 to 1.3 to lead by 39 points at the main break.
Newcombe importantly kicked the opening goal of the second half to reassert the Hawks' authority and they powered clear for a convincing win in front of 68,515 fans.
The margin gave their percentage a significant boost - from 117.6 to 121.2 - which could be important in a tight finals race.
Watson was a constant threat in the forward-line and captain James Sicily led a tight defensive unit, with Jarman Impey (25 touches) influential and Jack Ginnivan (27) busy without hitting the scoreboard against his former club.
