about the knee




The knee has a difficult task: transferring body load while simultaneously allowing the body to rapidly change speed and direction. The necessary twisting and rotation stresses the joint. Certain activities subject the knee to nearly 10 times body weight - a good reason to keep body weight optimal!

The Knee Joint

Three bones and two different types of cartilage make up the knee joint. Let’s look
at some of these structures.

Femur, or thigh bone. The thigh bone ends at the knee with two separated prominences called condyles. Touch your knees together and you have brought the inside, or medial femoral condyles together. We call the outside condyle the lateral femoral condyle.

Tibia, or shin bone. The top of the tibia meets the femur with a tibial plateau. The medial condyle rides on the medial plateau on the inside; on the outside the lateral condyle rides on the lateral plateau.

Patella, or knee cap. This small bone rides in the groove, or sulcus between the condyles. The sulcus sits over the front part of the femur just above the condyles in an area called the trochlea.

Articular cartilage. A glistening white substance like firm rubber covers the end of the femur., the top of the tibia, and back of the patella. These special articular cartilage surfaces glide, or “articulate,” together. We call this special cartilage hyaline cartilage, a mixture of collagen and sponge-like molecules, all maintained by living cells. Hyaline cartilage creates a surface more slippery than water on ice. When healthy, this allows smooth, easy joint motion.

Meniscal cartilage. On top of the plateau are two C-shaped pads, each called a
meniscus, that cushion the contact between the thigh bone and the shin bone. On
the inside is the medial meniscus and on the outside, the lateral meniscus. This
cartilage, comprised of fibro-cartilage, differs from hyaline cartilage.

Injuring either type of cartilage upsets the normal stresses on the knee. These
injuries might not result from trauma but merely from normal daily activity. Upsetting
the delicate balance of forces on the knee produces abnormal loads that create
“overload damage.” Gradually, small defects in the articular or meniscal cartilage
degenerate into more severe joint disease, a type of osteoarthritis.

The meniscus: new approaches »


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