Learning About Your Knee Condition

The knee has the difficult task of transferring the weight-bearing load of the body while at the same time having the freedom to allow rapid change of direction and speed. This necessary twisting and rotating adds to the stress the joint endures.

The knee joint is made up of three bones, four major ligaments groups, and two different types of cartilage.

Bones

The bones in the knee are the femur, tibia, and patella.

Femur (thigh bone)

At the knee joint, there are two separated prominences called condyles. Touching your knees together brings the inside condyles closer together--the medial femoral condyles. The outer condyle is the lateral femoral condyle.

Tibia (shin bone)

The tibia meets the femur at the knee with two areas on which the two femoral condyles “ride.” These are the medial and lateral tibial plateaus.

Patella (knee cap)

The patella rides in a shallow groove (or sulcus) over the front part of the femur called the trochlea.

Ligaments

Ligaments are tough, fibrous bundles which are strong but only slightly elastic. Each ligament connects the femur to the tibia or fibula at a different point. The ligaments in the knee are:

Medial and Lateral Collateral Ligaments (MCL and LCL)

The MCL is found on the inner side of the knee joint, the side closer to the other knee. The LCL is found on the outer side of the knee joint, the side further away from the other knee. Collateral ligaments are on the outside of the joint.

Anterior and Posterior Cruciate Ligaments (ACL and PCL)

The ACL is found closer to the front of the knee, and the PCL closer to the back. Cruciate ligaments cross each other on the inside of the knee.

Cartilage

There are two types of cartilage in the knee: articular and meniscal

Articular Cartilage

Articular cartilage covers the ends of bones at the knee joint. This glistening white substance has the consistency of firm rubber but is actually a mixture of collagen and special large sponge-like molecules all maintained by living cells (chondrocytes). With normal joint fluid, the surface is more slippery than ice on ice. This allows for normal smooth and easy joint motion.

Meniscal Cartilage

Meniscal cartilage is best described as C-shaped pads found between the thigh bone and shin bone--one at each side--called the medial meniscus (inner thigh aspect) and lateral meniscus (outer). They are attached for the most part to the top of the tibia or tibial plateaus. They serve to cushion and transfer joint force. They accomplish this by distributing joint forces over a larger area of the joint, transferring force from the curved femoral condylar margins to the flatter tibial plateaus.