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 before being taken to hospital for precautionary scans.
"He was non-responsive for a little while and we were all really worried about him," Collingwood football manager Charlie Gardiner told the Seven Network at halftime.
"But once the doctors got him down into the rooms he was up and walking around.
"I don't think there are any other concerns (aside from concussion). They just want to rule everything out and take every precaution possible."
Hawks midfielder Newcombe (28 disposals, seven clearances) was also groggy after the collision 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.
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.
Hawks ruckman Lloyd Meek kicked three goals in an outstanding display, with Watson a constant threat in the forward-line and captain James Sicily important in a tight defensive unit.
Jack Gunston (four goals) and Mabior Chol (three) were dangerous, and Jack Ginnivan (27 disposals) was busy without hitting the scoreboard against his former club.
Collingwood's heavy defeat was a disappointing way for club great Steele Sidebottom to mark his 350-game milestone.
