Instability of the knee joint—medial or anteromedial?: From anatomy to treatment

Abstract

Background: Injuries of the medial collateral ligament complex are one of the most frequent knee injuries. They can frequently be treated conservatively with good clinical results; however, persisting instability results in increased load on the cruciate ligaments and especially by their involvement need adequate treatment. Anatomy and biomechanics: The medial collateral ligament complex essentially consists of the superficial collateral ligament (sMCL), which is the primary stabilizer against valgus, the deep collateral ligament (dMCL) with its anterior obliquely running ventral part (AML), which are only secondary stabilizers against valgus but primarily stabilize against external rotation, and the posterior oblique ligament (POL), which stabilizes against valgus and internal rotation in full extension. Treatment: Chronic instability and higher grade injuries with dislocation of the ligament stumps and multiligamentous injuries require surgical treatment. In the acute setting avulsion injuries show excellent healing capacity if anatomic refixation is performed; however, for intraligamentous injuries suturing of the ligament with additional tendon augmentation is recommended. In chronic instability it is crucial to distinguish the different instability patterns to opt for the appropriate reconstruction technique (sMCL reconstruction alone or combined sMCL + AML reconstruction). In both situations the technique described here using a flat tendon graft more closely resembles the native anatomy than conventional techniques. Discussion: Reconstruction techniques using flat tendon grafts that address all affected parts of the ligament, showed high biomechanical efficacy in sufficiently treating complex medial instability. If they are also clinically superior has to be shown in further clinical studies.