Posterior oblique ligament of the knee: state of the art
The posterior oblique ligament (POL) was described for the first time by Hughston and Eilers in 1973 who assigned clinical and biomechanical significance of the knee’s stability to it.1 Subsequently, however, Robinson et al, in their dissection study, did not find a discrete ligament, and they simply referred to all structures posterior to the superficial medial collateral ligament (sMCL) as the posteromedial joint capsule.2 Biomechanics and cadaveric studies have demonstrated that the POL can be considered to be the predominant ligamentous structure on the posterior medial corner of the knee joint. It is located at the posterior third of the medial collateral ligament, attached proximally to the adductor tubercle of the femur and distally to the tibia and posterior aspect of the joint capsule.3 The main role of the POL is to control anteromedial rotatory instability (AMRI) and to provide static resistance to the valgus loads when the knee is fully extended. Moreover, the POL plays a small role in preventing posterior translation of the tibia on the femur because the posterior cruciate ligament (PCL) is so overpowering.4 During a side-step cut, the POL contributes to keeping the pivot leg from opening in valgus, possibly acting in synergy with semimembranosus (SM) muscle activation. Additionally, the POL helps prevent excessive external tibial rotation and internal femoral rotation. Investigating the extent of injury to the POL and posterior capsule is important in decision-making because the non-operative treatment of these injuries may more likely lead to unsatisfactory results.5 The resulting rotational instability, in addition to valgus laxity, may not be tolerated by athletes participating in pivoting sports.6 This narrative review aims to demonstrate that the POL is the predominant structure in the posteromedial corner of the knee joint (PMC) and that surgical reconstruction should be considered the gold standard treatment in case of injury. Further, we analysed the best imaging and surgical strategies in the setting of POL lesions.