Anterolateral ligament of the knee: myth or reality?

A ligament of the knee has recently drawn the attention: the rediscovered anterolateral ligament (ALL) of the knee. The tibial insertion of the ALL is torn off in the Segond fracture, pathognomonic of the anterior cruciate ligament tear. The ALL originates from the lateral femoral epicondyle and has fibers inserting on the lateral meniscus. It attaches distally to the tibial plateau, midway between the tip of the fibular head and Gerdy's tubercle. The purpose of this study was to evaluate the visibility of the ALL using routine MRI (1.5T) protocol.

In the first part of our study 10 cadaveric knee joints were examined using MR imaging to evaluate the visibility of the ALL. These cadaveric knees have been dissected to assess the presence of the ALL and to evaluate the accordance between MRI and anatomic dissection. In the second part of the study, 61 knee MRI of patients were examined to evaluate the visibility of the ALL using axial and coronal DP-FS weighted sequences.

In all cadaveric knee MRI, the ALL was visualized (full visualization in 75 % and partial visualization in 25 % of the cases), with 100 % accordance between MRI and anatomic dissection. Two cadaveric knees where the ALL was not viewed were excluded of the radio-anatomic analysis. The ALL was visualized in 93.4 % (95 % CI = 84.1-98.2) of the knee MRI studies of the 61 patients included. The whole ligament was visualized in 82 % (95 % CI = 70-90.6) examinations and it was partially visualized in 11.5 % (95 % CI = 4.7-22.2).

Our results show that the ALL of the knee can be identified using routine 1.5T MR imaging, which suggest that better radiological description of this underestimated anatomical structure may be beneficial in the preoperative planning of ACL tears.