The addition of Orton boosts the team's roster to 20 players.
The 6-foot-10 Orton left Kentucky after his freshman year and was drafted 29th overall by the Orlando Magic in 2010.
Last season, Orton played for the Oklahoma City Thunder and its Developmental League affiliate, the Tulsa 66ers. With Tulsa, he averaged 12 1/2 points, eight rebounds and more than two blocks per game.
The Washington Wizards have waived center D'Or Fischer to reduce their roster to 18 players.
The 6-foot-11 Fischer, 32 and an undrafted free agent, has played in Europe since he came out of West Virginia in 2005. He signed with Washington on September 28.
The Denver Nuggets have announced forward Reginald Becton and guard Kyle Fogg were waived to trim the roster to 16 players.
An undrafted free agent from Arizona, Fogg played in the NBA Developmental League last season with the Rio Grande Valley Vipers.