The knee
joint is made up of three bones and a variety of ligaments. The knee is formed
by the femur (the thigh bone), the tibia (the shin bone), and the patella (the
kneecap). Several muscles and ligaments control the motion of the knee and
protect it from damage at the same time. Two ligaments on either side of the
knee, called the medial and lateral collateral ligaments, stabilize the knee
from side-to-side.
The anterior cruciate ligament (ACL) is one of a pair
of ligaments in the center of the knee joint that form a cross, and this is
where the name "cruciate" comes from. There is both an anterior cruciate
ligament (ACL) and a posterior cruciate ligament (PCL). Both of these ligaments
function to stabilize the knee from front-to-back during normal and athletic
activities. The ligaments of the knee make sure that the weight that is
transmitted through the knee joint is centered within the joint minimizing the
amount of wear and tear on the cartilage inside the knee.
The weight-bearing surfaces of your knees are covered
with a layer of cartilage (referred to by doctors as"articular cartilage").
There are also two shock absorbers in your knee on either side of the joint
between the cartilage surfaces of the femur and the tibia. These two structures
are called the medial meniscus and the lateral meniscus. The menisci are
horseshoe-shaped shock absorbers that help to both center the knee joint during
activity and to minimize the amount of stress on the articular cartilage. The
combination of the menisci and the surface cartilage in your knee produces a
nearly frictionless gliding surface. The knee is an incredible joint. It is
strong, flexible, and very tough.
Knee
Stability
The stability of the knee joint
is maintained by four ligaments, thick bands of tissue that stabilize the joint.
The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are
on the sides of the knee and prevent the joint from sliding sideways. The
anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) form an
"X" on the inside of the knee and prevent the knee from sliding back and forth.
These limitations on knee movement allow the knee to concentrate the forces of
the muscles on flexion and extension.
Inside the knee, there are two
shock-absorbing pieces of cartilage called meniscus that sit on the top surface
of the tibia. Each meniscus allow the femoral condyle to move on the tibial
surface without friction, preventing the bones from rubbing on each
other.
Bursas surround the knee joint and are fluid filled sacs that
cushion the knee during its range of motion. In the front of the knee, there is
a bursa between the skin and the kneecap called the prepatellar bursa and
another above the kneecap called the suprapatellar bursa.
