Joakim Noah successfully underwent minor arthroscopic surgery to clean out his left knee. The 2013-14 Defensive Player of the Year was dealing with knee pain through the second half of the season, but played like the best center in the League during that stretch. From NBA.com:

The Chicago Bulls announced today that center Joakim Noah successfully underwent minor arthroscopic surgery to clean out his left knee. The procedure was performed at Rush Oak Park Hospital by Chicago Bulls head team physician Dr. Brian Cole. He is expected to rehab his left knee during the offseason for the next eight to 12 weeks.