1.Bones
Four bones meet to form your knee: your thighbone (femur), shinbone (tibia), the smaller bone that runs alongside it (fibula), and kneecap (patella). Any of them could crack (fracture) or break. Or a small piece might break off. You may also dislocate or move one of these bones out of place, especially your kneecap.
2.Ligaments
These tough, fibrous, stretchy cords connect one bone to another. They also help strengthen and bind joints together. They allow movement in some directions but prevent it in others. The knee has two main types. Collateral ligaments control sideways motion and keep your knee from moving in the wrong way. Cruciate ligaments are inside the joint and help it move forward and backward.
