Anterior cruciate ligament (ACL) is the most commonly injured knee ligament. It connects the thigh bone to the shin bone.
Posterior cruciate ligament (PCL) also links the thigh bone to the shin bone in the knee.
Lateral collateral ligament (LCL) connects the thigh bone to the fibula, the smaller bone of the lower leg on the outer side of the knee.
Medial collateral ligament (MCL) links the thigh bone to the shin bone on the inside of the knee.