Bones are linked to other bones by ligaments. You can find four Key ligaments in your knee. They act like powerful ropes to hold the bones with each other and keep the knee steady. This title is fitting as the ACL crosses the posterior cruciate ligament to variety an "X". https://dr-bakul-arora.mystrikingly.com/blog/knee-ligament-injuries-a-comprehensive-guide-to-understanding-treating-and