BOSTON — Andrew Bynum is altogether clear on this: He'll play in Game 5 of the NBA finals.
Beyond that, the key to the Los Angeles Lakers' interior defense — and perhaps the team's championship chances — can't make any promises.
"I'm 100 percent sure that I'm playing come Sunday," the Lakers' 7-foot center said Saturday.
Bynum had fluid drained from his right knee after Boston evened the series 2-2 with a 96-89 win Thursday night. He was encouraged that the swelling had not returned since then. He had fluid drained from the same knee just before the series and the swelling reappeared.
He knows that will happen again.
"It's going to come back after Game 5, for sure," Bynum said. "It's guaranteed. But as long as I'm able to be out there and be effective, that's what counts. And I know this game is the biggest game because it can change the whole series."
Bynum played 28 minutes in the opener, 39 in the second game and 29 in the third. He had 40 points and 22 rebounds as the Lakers opened a 2-1 series lead. But he played just 12 minutes in Game 4 and sat out the last 14 minutes. His totals: two points, three rebounds, no blocks.
Without him, the Lakers let a 62-60 lead after three quarters slip away as Boston power forward Glen Davis took advantage of Bynum's absence to score nine points in the fourth quarter. Two of Davis' baskets helped turn a 64-all tie into a 70-64 lead.
"It's rare that you see an NBA game won by one six-point run, and that's kind of what happened," Bynum said. "The whole game was real slow, real nasty. We had the lead and we kind of, so to speak, choked."
Had he played, it would have been much tougher for Davis to grab rebounds and make layups.
Bynum's health could be the difference between the Lakers successfully defending their title or the Celtics reclaiming it after beating Los Angeles in 2008.
"I embrace the responsibility," he said, "because I know what I'm able to do out there on the court and just want to go out there and just be effective. If I do that, if I give us some good minutes out there, then we'll have a great shot at winning the game."
Bynum doesn't know how long he'll play Sunday. That depends on how he feels. He does know he wouldn't be able to play if the fluid had not been drained.
"I'm going to be able to play with the pain. That's not the problem," he said. "It's when the swelling's in there … it shuts the muscle down and then that's when you're really vulnerable to more injury."
Bynum has a torn meniscus and bone bruise in his knee. Surgery is scheduled for July with an expected rehabilitation period of two to five weeks, he said.
Meanwhile, he plays on.
"He's made the ultimate sacrifice and tried to pay the ultimate price," Lakers guard Derek Fisher said. "As a professional basketball player, your commodity is your body. So for him to take the steps that he's taking to try and help us win, I think that says a lot about who he is and what his purpose is with our team."
Bynum, 22, was 17 when the Lakers made him the youngest player ever drafted in the first round. His scoring average has increased in each of his five seasons, to 15.0 this season along with 8.3 rebounds.
Without him, the Lakers' only consistently effective inside player is 7-foot Pau Gasol.
"He's been a factor when he's been out there," Gasol said. "It also helps me to have him there just because of his presence and his length, his size, just rebounding, defending. Those two things are keys at this point because they've been the difference in the series."
Bynum planned to have more treatment on Saturday and be ready for the Celtics to test him on Sunday.
"That's what they're supposed to do," Bynum said. "They're supposed to attack, but I think we'll be ready."