The knee is a major weight-bearing joint that provides flexibility and mobility. Bones, ligaments, cartilage, muscles and tendons all work together to build a healthy knee. Here are the components of the knee, and how the knee functions.

Three Compartments

1. The inside (medial) compartment.
2. The outside (lateral) compartment.
3. The kneecap (patella) compartment.

The compartments work together to manage stress that the knee receives during daily activity.

Three Bones

1. Femur, also known as thigh bone
2. Tibia, also known as the shin bone
3. Patella, also known as the kneecap

The femur and tibia meet to form a hinge with the patella. The patella sits over the femur and the tibia to protect the joint.

Two Types of Cartilage

1. Menisci
2. Articular cartilage

Articular cartilage is an elastic material that covers the ends of the femur, top of the tibia and the underside of the patella. Articular cartilage allows the joint to move smoothly and gives the knee shock relief.

Two structures known as menisci sit between the femur and the tibia and act as cushions or shock absorbers for the knee. The menisci are pads of cartilage that further stabilize the bones.

Four Ligaments

1. The medial collateral ligament (MCL), which runs along the inside of the knee.
2. The lateral collateral ligament (LCL), which runs along the outside of the knee.
3. The anterior cruciate liagament (ACL), which is located in the center of the knee.
4. The posterior cruciate ligament (PCL), which is located in the center of the knee.

Ligaments hold the knee together. The medial (inner) collateral ligament (MCL) and outer (lateral) collateral ligament (LCL) limit sideways motion of the knee. The posterior and anterior cruciate ligaments (PCL and ACL) limit forward motion of the knee bones, keeping them stable. Ligaments run along the sides and front of the knee connecting the shinbone to the thighbone at the center of the knee, they provide stability for the knee. The ACL and PCL are what give the knee natural feeling during physical activity.

Two Groups of Muscles

1. The four quadriceps
2. The hamstring muscles

The quadriceps muscles straighten the knee and the hamstring muscles bend the knee.

Tendons

Tendons connect muscle to knee. The quadriceps muscles on the front of the thigh are connected to the top of the patella by the quadriceps tendon, which covers the patella and becomes the patellar tendon. The patellar tendon then attaches to the front of the tibia. The patella is the moveable bone on the front of the knee. It is wrapped inside a tendon that connects the large muscles on the front of the thigh, the quadriceps muscles, to the lower leg bone.

9/24/2008