Anterior cruciate ligament (ACL) lesion is a frequent injury in sport activities, particularly in high-contact sports. ACL functional insufficiency causes an increased anterior tibial translation (straight or primary instability) and an increased internal tibial axial rotation. Single-bundle ACL reconstruction was indicated by the literature and by the largest number of orthopaedic surgeons as the gold standard for acute or chronic ACL lesions, which could be easily diagnosed through clinical examination and magnetic resonance imaging (MRI). Rotational instability of the knee consequent to an ACL lesion is a stimulating argument both from a biomechanical point of view and from a surgical one. Clinically, rotational instability is referred to as a bi-axial combined instability during cutting movements, mainly during fast changes of directions such as a football player performs in dribbling. Hugston  classically distinguished anterior rotational instability in: - Anteromedial rotational instability (AMRI) due to a lesion of the medial compartment, including posterior oblique ligament (POL) ruptures. AMRI is increased in associated ACL lesions; - Anterolateral rotational instability (ALRI) caused by a tear of the central third and the lateral capsular ligament. Also, ALRI is empowered by associated ACL lesions. ACL functional insufficiency has been indicated as the main cause of AMRI, most of all with the knee near to its complete extension; however, several biomechanical studies reported in the current literature have shown that the medial collateral ligament (MCL) plays an important role in anteromedial rotational stabilisation, mainly at 30? of flexion. An unrecognized MCL instability consequent to a grade 3 MCL lesion can be a predisposing factor for ACL reconstruction failure. In fact, chronic MCL deficiency has been noted to increase stress on an ACL graft, particularly during the critical interval of the neoligamentisation . Moreover, other authors have demonstrated that associated ligamentous functional deficit either not discovered or underestimated in preoperative planning can represent the main causes of ACL reconstruction failure .
ASJC Scopus subject areas