Anatomy and magnetic resonance imaging of the posterolateral structures of the knee.

The purpose of the present study was to provide detailed information of the morphological and radiological characteristics of the posterolateral structures of the knee. Muscles and ligaments of the posterolateral part of the knee were studied by dissections of 50 adult cadaver knees and by Magnetic Resonance Imaging (MRI) before and after dissections for comparisons. Diverse morphological characteristics of the arcuate ligament were found. The fabellofibular ligament was present in 42.1% of the knees dissected, whereas the popliteofibular ligament was found in 37.5%. A ligamentous structure, which could be called the posterior tibial ligament, was found in 31.6% of the cases that originated from the lateral part of the capsule proximally and inserted distally on the mid portion of the proximal tibia. By comparing the cross sections and the dissections of the cadaver knees, the popliteus muscle, the arcuate ligament, the fibular collateral ligament, the popliteofibular ligament, and the fabellofibular ligament could be identified in MRI. Comprehensive understanding of the posterolateral anatomy of the knee and improved identification of the structures in MRI will help clinicians to make a more accurate and noninvasive diagnosis of posterolateral instability.