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Let's begin with the basics of knee anatomy. 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.
Movement of the knee
The main muscles that move the knee joint are the quadricep
and hamstring muscles. The quadriceps attaches to the patella, and the
patellar tendon connects this muscle to the front of the tibia. When the
quadricep muscles contract the knee extends. In contrast, when the hamstring
muscles contract, they pull the knee into flexion. |
