"The basketball community has lost a Legend. Our hearts are with the family, friends and fans of Willis Reed," the organization wrote on Twitter.
Reed spent his entire 10-year career with the Knicks, and he had his No. 19 retired by the organization in 1976, two years after he retired.
He was the first player to ever have his number retired by the organization, and he later served as their head coach.
Willis Reed #19 of the New York Knicks pulls down the rebound during the Eastern Conference Finals played in 1973 at the Boston Garden in Boston, Massachussetts. (Dick Raphael/NBAE via Getty Images)
He was named to the Naismith Basketball Hall of Fame in 1982, but perhaps he is best known for coming out of the tunnel while nursing a severe thigh injury before Game 7 of the 1970 NBA Finals.
Reed got injured in Game 5 and missed the next contest, but he surprised all in attendance when he came out for Game 7's warmups, and he scored the Knicks' first two baskets of the game. They were the only points of the game for Reed, but the Knicks won the game, 113-101 to take home their first championship over the Los Angeles Lakers.
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Reed was named the MVP of that Finals and had won the regular season MVP, as well. Before his injury, he put up 31.8 points and 15.0 rebounds in the series' first four games. He also helped the Knicks to another title in 1973 which he again won the Finals MVP.
New York Knicks Legends Willis Reed is seen during the game between the Memphis Grizzlies and the New York Knicks on October 29, 2016 at Madison Square Garden in New York City, New York. (Nathaniel S. Butler/NBAE via Getty Images)
The seven-time All-Star averaged 18.7 points and 12.9 rebounds per contest in his career that was cut short by injuries - he was named to both the NBA's 50th and 75th Anniversary Teams.