O'Quinn was acquired from Orlando by a sign-and-trade. The Knicks gave the Magic the right to exchange 2019 second-round draft picks and cash considerations.
Team President Phil Jackson said Thursday the players will provide ''veteran leadership, talent and youth,'' and along with first-round draft picks Kristaps Porzingis and Jerian Grant ''will make for a very competitive team this coming year.''
The Knicks were a franchise-worst 17-65 last season.
Afflalo averaged 13.3 points for Denver and Portland last season. The 7-foot Lopez averaged 9.6 points and 6.7 rebounds for the Trail Blazers and will provide an inside presence defensively.
General manager Steve Mills says the Knicks ''addressed our primary needs this offseason by adding size and versatility.''