Advent International has announced it will acquire a majority ownership interest in ATI Physical Therapy (ATI) from KRG Capital Partners.

ATI, headquartered in Bolingbrook, Ill., is a privately held healthcare company specializing in outpatient rehabilitation and adjacent healthcare services. It has more than 500 locations in the continental United States.

Advent International, with U.S. offices in Boston and New York, is a global private equity firm founded in 1984 that focuses on investments in five core sectors: business and financial services; healthcare; industrial; retail, consumer and leisure; and technology, media and telecom.

KRG Capital Partners, based in Denver, was founded in 1996. It is a middle market private equity firm focused on investing in specialty distribution, marketing services, specialty manufacturing and business services.

Financial terms of the transaction were not disclosed. The transaction is expected to be completed in the second quarter of 2016.