They scrap, they fight, they dig in, they hound, they harass, and it all amounts to a waste of time when, after all that determined work, they don’t do something quite basic.

They don’t get the ball.

“We can’t go out there and give that type of effort defensively and then let it go for nothing by not getting the ball,” Latrell Sprewell said.

It’s happening at an alarming rate for the Knicks, who can feel more relieved than rejuvenated by yesterday’s 91-83 victory over the Heat at the Garden. Once again, the Knicks were mauled on the boards, outrebounded 48-37. In the four games, the Knicks have been beaten off the glass by one, seven, 11 and 11, adding up to a minus-30, which won’t add up to the Knicks escaping a series that now is down to a best-of-three heading back to Miami.

“They dominated us on the boards overall,” Jeff Van Gundy said. “And if they are going to continue to do that, it’s going to be very, very difficult to find a way to manufacture enough points, because you are always playing too long on the defensive end.”

There was a twist to the latest rebounding follies yesterday as the Knicks did a much better job on the offensive boards (13) but pulled in only 24 defensive rebounds, leading to 16 offensive rebounds for the Heat. That’s a ton of second and, at times, third shots. They couldn’t keep Alonzo Mourning (six) or Dan Majerle (four of his 12 total rebounds) from crashing the offensive glass.

Van Gundy ripped into his team for their wimpy rebounding after the Game 3 loss, but there was no turnaround and only marginal improvement.

“What we have to do is make a more concerted effort of boxing out,” said Patrick Ewing, who had a team-high 11 rebounds. “We are rotating, and I got to stay on Zo a little bit more. I am trying to help maybe a little too much and leaving him wide open on the rim, and he is taking advantage of it.”

There was a plea by Van Gundy to get his guards to get bodies on the bigger, stronger Miami frontcourt players, and whirlwind Charlie Ward did have seven rebounds. But Sprewell had just one and Allan Houston had only three. Larry Johnson is having all sorts of problems keeping P.J. Brown from swarming in for rebounds.

“These guys are giving it to us on the boards, there’s no other way to put it,” Sprewell said. “We have to do something about that. You’ve got to hit first, and often. You can’t let them keep running in there, getting those boards. If you have to take a foul, you have to take a foul. As good as we’re playing on defense, it’s all going to waste because we’re not getting the rebound and going the other way.”