The healthy knee is a complex hinge joint consisting of bones and healthy cartilage. The three bones that form the knee are the thighbone (femur), shinbone (tibia), and kneecap (patella). The femur and tibia are held together by ligaments, which are strong bands of tissue that stabilize the joint.
The end of your femur can be compared to a rocking chair. It has two distinct surfaces called compartments, which rest on the tibia. The third compartment is found behind the patella. All three compartments are covered with a tough lubricating tissue called cartilage.
Cartilage acts like a natural shock absorber, preventing bone on bone contact and providing a smooth, pain-free surface for the bones to glide against. The knee also contains synovial membranes, which produce synovial fluid to help lubricate and nourish the cartilage.