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The largest joint in the body, the knee is
also one of the most complex. It is made up of bones, tendons, ligaments and
cartilage.
Bones
The bones of the knee are the femur (thigh
bone), tibia (shin bone) and patella (kneecap). The femur and tibia meet to
form a hinge with the patella in front of these two bones protecting the joint.
The patella slides up and down in a groove in the femur (the femoral groove) as
the knee is bent and straightened.
Ligaments
Ligaments hold the knee together and give it
stability. 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 backward and forward motion of
the knee bones, keeping them stable.
Cartilage
Two structures known as menisci sit between
the femur and the tibia and act as cushions or shock absorbers for the knee. A
torn meniscus is often referred to as "torn cartilage." Menisci are
one of two types of cartilage in the knee. The other type, articular cartilage,
is a smooth and very slick material that covers the end of the femur, the
femoral groove, the top of the tibia and the underside of the patella. This
articular cartilage allows the bones to move smoothly.
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
hamstring muscles in the back of the leg attach to the tibia at the back of the
knee. The quadriceps muscles straighten the knee and the hamstring muscles bend
the knee. Bones, ligaments, cartilage and tendons all work together to build a
healthy knee.
©2003
Smith & Nephew, Inc. Used with permission.
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