The knee joint is made up of three bones:
1. the thigh bone (femur)
2. the leg bone (tibea)
3. the knee cap (patella)
The knee joint is like a ‘hinge’. It is made up of two joints. The thigh bone (femur) in your upper leg is hinged to the shin bone (tibia) in your lower leg. This is called the femorotibial joint. Where the thigh bone (femur) connects with the knee cap (patella) it is called the patellofemoral joint. These two joints allow you to bend and straighten your knee.
In a normal knee, the surfaces of all three bones coming into contact with each other are covered with a smooth gliding surface. This smooth substance is known as the articular cartilage. It provides a smooth surface to let you easily move around, and it acts as a shock absorber for any stress placed on the knee.
When the knee is healthy, the knee joint moves freely. But disease or injury can wear away the cartilage between the bones in your knee joint. Without this cushioning, the bones can become rough and rub together, causing pain.
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