Cartilage is not dense enough to be seen on an x-ray. The knee is a synovial joint. The tissue lining the joint, called synovium, produces fluid that lubricates and nourishes the surfaces of the joint. The important internal parts of the knee include articular cartilage, meniscal cartilage, ligaments, and tendons . There are two types of cartilage in the knee.
Articular cartilage is specialized tissue that covers the ends of the bones.
Meniscal cartilage is specialized tissue located around the perimeter of your knee. It helps to distribute the load and provide some stability as well as lubricate the articular cartilage. There are also several tendons, which are also strong bands of fibrous tissue, but they attach muscle to bone. It is the force of the quadriceps and hamstring muscles, pulling through tendons, that move the knee and enable you to walk, sit, get up from sitting, climb stairs, etc.