Shane Carwin has had enough.

The 38-year-old engineer by day has announced his retirement from MMA. Carwin finished his career 12-2 and is a former interim UFC heavyweight champion.

Carwin has underwent neck, back and knee surgery since 2010, and has not fought since a loss to Junior dos Santos in 2011. He served as a coach on The Ultimate Fighter late last year, but was forced out of a planned bout with Roy Nelson.