The posterior cruciate ligament consists of two functional bands: the anterolateral band (ALB, larger, approximately 70% of PCL cross-section) which tightens in flexion and is the primary restraint to posterior tibial translation at 90 degrees; and the posteromedial band (PMB, smaller) which tightens in extension and contributes to stability at lower flexion angles. The meniscofemoral ligaments of Humphrey (anterior) and Wrisberg (posterior) reinforce the PCL complex.
The ALB is the primary restraint to posterior tibial translation in mid-flexion; the PMB provides additional restraint at near-extension angles; together they prevent posterior drawer and external rotation instability of the tibia.
PCL reconstruction techniques have evolved to address both bundles: single-bundle reconstruction using the central PCL footprint addresses the dominant ALB; double-bundle reconstruction attempts to reconstruct both the ALB and PMB bundles to more closely restore native PCL kinematics. The PCL femoral attachment on the medial femoral condyle is larger and more complex than the tibial attachment, and accurate tunnel placement for both bundles requires a thorough understanding of the two-band anatomy. Isolated PMB tears at low flexion angles may be missed unless the PCL is examined in extension.
Complete PCL rupture produces a positive posterior drawer and increased posterior tibial translation at 90 degrees flexion from ALB failure; double-bundle reconstruction with separate ALB and PMB grafts placed at the native PCL footprints aims to restore both flexion and extension posterior stability, though clinical outcomes improvement over single-bundle reconstruction remains debated.
