The move was made Tuesday. To make room on the roster, the Lynx waived guard Lindsey Moore, their first-round draft pick last year.
McKenith played in 32 games for Washington as a rookie last season, averaging 2.8 points, 1.1 rebounds, 1.0 assists and 8.8 minutes. She was a second-round draft pick out of St. John's but waived in May after training camp.
Moore played sparingly as a rookie out of Nebraska, and the signing this year of veteran guard Tan White further limited her opportunity in a reserve role behind Lindsay Whalen, Seimone Augustus and Monica Wright.
The Lynx play at the Seattle Storm Friday.