The knee is a hinge joint where three bones meet: the upper part of the shin bone (tibia), the lower part of the thigh bone (femur), and the kneecap (patella). The cartilage is a smooth covering on the ends of the bones that allows the joint to move easily and absorbs shock. The two pads (menisci) in the knee joint (one on the inner side and one on the outer side) also assist with shock absorption. The knee joint has oblique (cruciate) ligaments inside the knee joint and collateral ligaments surrounding the joint to provide stability. There are two cruciate ligaments: the anterior cruciate ligament and the posterior cruciate ligament. There are also two collateral ligaments: the inner (medial) and the outer (lateral) collateral ligaments.