ascertained, attained, chained, contained, drained, entertained, entertained, feigned, ingrained, maintained, ordained, pained, restrained, retained, retained, stained, strained, sustained, trained, unconstrained.
Your query has returned 1657 words, which include anagrams of constrained as well as other shorter words that can be made using the letters included in constrained.
The words in this list can be used in games such as Scrabble, Words with Friends, Wordscapes and other similar games.