Coach Mike Woodson said each player is likely to miss multiple games, a big blow to the Knicks' depth.
"We've got to suck it up," Woodson said.
Martin sprained his troublesome left ankle early in the second quarter and was ruled out for the remainder of the game. The team had no immediate update on his condition afterward.
"It hurts any time Kenyon's not out there," Woodson said. "He gives us that toughness and added defense we need."
Martin appeared to collide with Pacers guard Lance Stephenson and checked out with 9:41 remaining in the period. A trainer attended to Martin as he walked back to the locker room.
Martin sat out three games earlier this season due to soreness in the left ankle. He also missed three games because of a strained abdominal muscle. The 6-foot-9 veteran of 13 NBA seasons was scoreless in 7:10 against the Pacers. He had been playing well, collecting 22 points and 23 rebounds in New York's previous three contests.
X-rays on Stoudemire's ankle were negative. He said the injury will be re-evaluated on Friday, and that he will consult with a team physician to decide whether an MRI is necessary.
"Right now, it's throbbing pretty good because the trauma happened not so long ago," Stoudemire said. "We'll sit down and see how it feels. I'm going to bounce back from this and get back to what I was before. Hopefully I'll be back sooner than later."
Stoudemire was hurt on a drive with 4:27 remaining in the third quarter. He stayed down for about a minute as six teammates and Woodson went over to the far corner of the court from the Knicks bench to check on him. Although Stoudemire stayed in the game and made 1-of-2 free throws, Raymond Felton committed an immediate foul on the inbound and Stoudemire was removed. The team announced shortly after that he would not return.
Carmelo Anthony said after the game that his understanding was that Stoudemire "sprained it really bad."