ligament (LCL) on the outer side of the knee. Two. ligaments cross each other (therefore, called cruciate) in the center of the knee joint: The crossed ligament toward. the front (anterior) is the ACL and the one toward the back. of the knee (posterior) is the posterior cruciate ligament (PCL). The ACL prevents the lower bone (tibia) from sliding forward. oo much and stabilizes the knee to allow cutting, twisting and. jumping sports. The PCL stops the tibia from moving backwards.