New York squandered an 11-point lead and Danny Ainge scored 10 points in a 24-7 third-quarter surge as the Celtics beat the Knicks, 115-108, last night in Boston to reach the 50-victory mark for the seventh consecutive NBA season.

Trailing, 43-32, the Celtics took the lead for good with a 21-4 run that gave them a 53-47 lead with 3:36 left in the first half. They led by 60-55 at halftime and by 71-66 with 7:52 to go in the third quarter.

Then Boston took control with the decisive 24-7 spurt that made the score 95-73 with 1:24 left in the period. The lead didn't drop below 10 points until the final minute.

Boston, whose 50-11 record is the NBA's best, won its eighth consecutive game, its 19th straight at home.

New York lost its 13th in 15 games.

The Celtics were led by Kevin McHale's 20 points and Dennis Johnson's 19. Rory Sparrow paced the Knicks with 17 points. Bucks 125, 76ers 95

Ricky Pierce and Terry Cummings each scored nine points during a 35-16 third-quarter burst that carried Milwaukee past visiting Philadelphia.

Charles Davis led the Bucks with 21 points.

Bob McAdoo had 20 for Philadelphia. Hawks 112, Bulls 108

Dominique Wilkins scored 42 points and Kevin Willis had 19 points and 21 rebounds to lead Atlanta to a come-from-behind victory in Chicago.

George Gervin led Chicago with 37 points. Spurs 142, Clippers 126

In San Antonio, Alvin Robertson scored 30 points and pulled down 11 rebounds, helping San Antonio beat Los Angeles and end a seven-game losing streak.

Norm Nixon led Los Angeles with 33 points, including a team-record six three-point baskets. Trail Blazers 125, Mavericks 114

Kiki Vandeweghe scored 34 points and Portland pulled away from visiting Dallas in the final period. Portland outscored Dallas, 19-4, in 6 1/2 minutes for a 114-98 lead with 4 1/2 minutes remaining. Jim Paxson had eight points, three steals and two assists during the spurt.

Mark Aguirre had 30 for Dallas. Pistons 104, Nets 102

In East Rutherford, N.J., Kelly Tripucka scored 34 points, including 15 in the fourth quarter, and Joe Dumars hit a crucial jump shot in the final minute as Detroit downed New Jersey.

King's 22 points led the Nets. Nuggets 134, Pacers 117

Alex English scored 34 points to lead Denver to an easy home victory over Indiana. Calvin Natt (20 points) broke a 6-6 tie two minutes into the game and the Nuggets never trailed.

Herb Williams and Steve Stipanovich led the Pacers with 21 apiece. Jazz 105, Suns 103

Adrian Dantley had 19 of his 36 points in the fourth quarter as visiting Utah beat Phoenix. Down, 87-77, with 11:02 left, Utah took the lead for good at 90-89 on Dantley's lay-up with 7:40 left.

Walter Davis had 24 points for the Suns. SuperSonics 120, Cavaliers 106

In Seattle, Jack Sikma scored 26 points and grabbed 12 rebounds and reserve Ricky Sobers added 19 points against Cleveland.

Sobers scored eight points and assisted on a basket to rally Seattle late in the third quarter.