Anatomy of the Knee
The knee is the largest, and one of the most complex, joints in the body. The knee has the challenging task of carrying and transferring the weight of the body, while at the same time bending, straightening and twisting in response to movement.
The knee joint is made up of 3 bones, 4 major ligament groups, and two different types of cartilage.
Bones
The femur is the large bone in the thigh, the tibia is the large shin bone and the fibula is articulating with the tibia. The patella, otherwise known as the knee cap, is the small bone at the front of the knee. The lower end of the femur has two “u” shaped ends known as the femoral condyles. These meet the tibia in two areas which are called the medial and lateral tibial plateaus.
Ligaments
Ligaments are like strong ropes that help connect bones together and provide joint stability. There are four main ligaments in the knee joint. On the inside of the knee (the side closest to the other knee) is the medial collateral ligament and on the outside is the lateral collateral ligament. The other two main ligaments, found in the centre of the knee, are the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). Smaller ligaments help hold the patella in place in the centre of the knee.
Cartilage
There are two types of cartilage in the knee, articular and meniscal.
Articular cartilage
Joint articular cartilage is a smooth, tough, rubbery material that covers the areas of the bones that come into contact with other bones. In the knee, articular cartilage covers the ends of the femur, the top of the tibia and the underside of the patella. Articular cartilage allows the bones to slide easily against each other as the knee bends, straightens and twists, and acts as a “shock absorber” in the joint.
Meniscal cartilage
Two C-shaped structures called menisci sit between the femur and the tibia. These structures made of fibrocartilage act as "cushions" or "shock absorbers". They also help provide stability to the knee. There is a medial meniscus and a lateral meniscus.