The knee joint is comprised of four bones;
patella (knee cap)
fibula (outside shin).
Cartilage covers the surfaces of bone where they come in contact with other bones.
Cartilage is incredibly smooth having at it has an incredibly low coefficient of friction – just 1/15th that of ice.
Where the top of the tibia comes in contact with the femur, it is known as the tibial plateau and its cartilage contacts that of the femoral condyles; two rams horn shapes separated by the intercondylar notch.
Both inside and outside of the femoral condyles the ligaments connect the femur and tibia together on top of which muscles and skin together form a knee joint.
Four major ligaments stabilize the knee joint.
The lateral collateral ligament (LCL) is located on the outside and connects the lateral femoral condyle to the head of the fibula.
The medial collateral ligament (MCL) is located on the inside and connects the medial femoral condyle to the medial tibia.
There are two cruciate ligaments, the anterior (ACL) and posterior (PCL).
The ACL and PCL limit the anterior (forward) and posterior (backwards) motion of the knee.
The ACL limits forward motion of the tibia and
the PCL limits backward motion.
Both ligaments also limit rotation of the tibia.
The C Shaped menisci help distribute the forces that are transmitted between the femur and tibia.
This helps to protect the cartilage that covers the ends of the femur and tibia.
Any of these structures can be injured (bones, ligaments, meniscus, cartilage). Fortunately, recent surgical advances allow us to repair or reconstruct much of the damage that may occur following an injury.