The Posteromedial Corner of the Knee: Anatomy, Pathology, and Management Strategies

Abstract

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.

Influence of posteromedial corner injuries on clinical outcome and second-look arthroscopic findings after allograft transtibial anterior cruciate ligament reconstruction

“…The MCL provides the primary valgus restraint in the flexed knee and is an external rotation stabilizer [ 20 , 21 ]. With extension, the PMC becomes the primary stabilizer to valgus stress and prevents posterior tibial translation [ 2 , 3 , 6 , 7 ]. Consequently, PMC injuries combined with ACL injuries are significantly different and more serious than isolated ACL rupture and make the knee unstable in valgus motion and rotations.…”

Posteromedial Corner Release with the Knee in Figure-of-Four Position vs Conventional Position for Varus Knee Arthroplasty

“…The goal can be achieved using soft tissue release and additional surgical techniques [17]. Subperiosteal release of the posteromedial corner structures is the conventional technique, but is often a cumbersome surgical procedure in severe varus knee [18].…”

Medial Collateral Ligament Reconstruction With Anteromedial Reinforcement for Medial and Anteromedial Rotatory Instability of the Knee

“…Whereas the injuries of the medial side of the knee are commonly identified with superficial medial collateral ligament (sMCL) tears, the anatomy and biomechanics of this region are complex 1 . The most important anatomic structures for the stability of the medial side of the knee involve the sMCL, the deep medial collateral ligament (dMCL), the posterior oblique ligament (POL), and other elements of the posteromedial corner 2 .…”

“…This structure is the main static stabilizer of the anterior one-third of the medial side of the knee and may be damaged during medial knee injuries, intensifying the medial and anteromedial rotatory instability (AMRI) caused by an sMCL tear 4 . It has been proven that the direction of AMRI, like the direction of the posterolateral rotatory instability, places an additional strain on intraarticular structures such as the anterior cruciate ligament (ACL) or the posterior cruciate ligament (PCL), which can lead to tears or reconstruction graft failures 1 . This is why we call medial knee instability together with AMRI the “hidden enemy” of cruciate ligaments and their grafts.…”

“…Because of the high potential to heal without surgery, surgical intervention in acute injuries is indicated only when a concurrent ACL or PCL tear exists and involves the acute repair or reconstruction of damaged medial structures 5 . For chronic valgus instability with medial gapping and multiligament injuries, surgical management is the method of choice and involves the reconstruction, rather than just repair, of the main medial stabilizers of the knee: the sMCL and the POL 1, 5, 6, 7, 8, 9. Currently, ∼28 surgical techniques for medial reconstructions exist, but only 1 is anatomic for the sMCL and allows restoration of “near-native” knee biomechanics in the coronal plane 7, 8.…”