What is your ACL and what does it do?

A ligament is a strong band of tissue that stops your joint from stretching too far. Your knee joint has four main ligaments, one on each side (the medial and lateral collateral ligaments or MCL and LCL), and two that cross over inside the joint (the anterior and posterior cruciate ligaments, or ACL and PCL). The ACL helps control the shin bone sliding forwards or twisting on the thigh bone.