Knee ligament anatomy

There are 4 major ligaments that stabilize the knee. The medial collateral ligament is on the inner side of the knee and the lateral collateral ligament on the outer side. The collateral ligaments give sideways stability to the knee. 2 ligaments cross in the centre of the knee. They are called the cruciate ligaments. The ligament towards the front is the anterior cruciate ligament, or ACL. And the one towards the back is the posterior cruciate ligament. The ACL prevents the lower bone, the tibia, from moving forward and the PCL prevents it from moving backward. If the ACL tears, the tibia can move forward too much and the knee can be unstable. The knee on which the ACL is torn tends to give out when pivoting or quickly changing direction. To correct this instability, a new ACL can be made. The strongest graft that is available to repair the torn ACL is the middle third of the patella tendon. This graft has a plug of bone taken from the patella, or knee cap, on one end and from the tibia on the other end. These plugs of bone are important because they provide solid fixation of the graft. This animation will explain how the middle third of the patella tendon is used to reconstruct a torn anterior cruciate ligament.