Former UFC interim heavyweight champion Shane Carwin announced his retirement Tuesday night.
"Officially retired," the 38-year-old Carwin said on Twitter. "Thank you to my family, friends and fans! God bless!"
Carwin, plagued by injuries for nearly two years, last competed inside the Octagon on June 11, 2011, at UFC 131. He lost a lopsided unanimous decision to then-titleholder Junior dos Santos.
After the fight, Carwin (12-2) injured his back during a training session. He would later undergo back surgery. He also underwent surgery to relieve recurring pain in his neck.
Carwin was slated to face Roy Nelson in December 2012, but pulled out of the bout after injuring a knee. He and Nelson were opposing coaches on Season 16 of "The Ultimate Fighter."
A hard-punching wrestler with good submission skills, Carwin finished each of his first 12 opponents in the opening round. He claimed the interim title in March 2010 at UFC 111 with a first-round knockout of former champion Frank Mir.
But his win streak came to an end in his next outing, a unification bout on July 3, 2010, at UFC 116 against lineal heavyweight champion Brock Lesnar. After a dominating first round, Carwin was submitted in the second by Lesnar.