The posteromedial corner of the knee encompasses five medial structures posterior to the medial collateral ligament. With modern MRI systems, these structures are readily identified and can be appreciated in the context of multiligamentous knee injuries. It is recognized that anteromedial rotatory instability results from an injury that involves both the medial collateral ligament and the posterior oblique ligament. Like posterolateral corner injuries, untreated or concurrent posteromedial corner injuries resulting in rotatory instability place additional strain on anterior and posterior cruciate ligament reconstructions, which can ultimately contribute to graft failure and poor clinical outcomes. Various options exist for posteromedial corner reconstruction, with early results indicating that anatomic reconstruction can restore valgus stability and improve patient function. A thorough understanding of the anatomy, physical examination findings, and imaging characteristics will aid the physician in the management of these injuries.