Magnetic resonance imaging (MRI) is the preferred imaging technique to evaluate the intact, ruptured or healed anterior cruciate ligament (ACL). However, its effectiveness in the diagnosis of chronic tears with synovialization has not been searched. During conservative treatment of torn ACL, there is a reparative process with proliferation of synovial scar tissue which may produce a bridge. This healing, so called synovialization, may cause ACL to be misdiagnosed as intact on MRI. This is true for old ruptures of ACL. Magnetic resonance imaging is reliable in the evaluation of acute ACL ruptures. However, MRI is not reliable to evaluate the stability of the healed ACL after conservative treatment, and the ruptures due to degenerated ACLs.