The knee is a lower extremity joint connecting the femur and the tibia. Because the knee is responsible for supporting almost the entire weight of the human body, the knee is especially vulnerable to injury and to the development of osteoarthritis.
The knee is a very complex joint, made up of bone, cartilage and tendons. The knee is actually made up of two separate joints. The femoro-patellar joint consists of the "kneecap" or patella, which sits inside the anterior thigh muscles tendons, and the patellar groove on the front of the femur bone through which it slides. The femoro-tibial joint connects the thigh bone, known as the femur, with the tibia, the large bone in the lower leg. One unique feature of the knee is that the joint is surrounded with a thick fluid found inside a membrane.
The knee also contains the following ligaments, which most sports fans could probably list off verbatim considering the high number of incidents of highly paid professional athletes tearing one or more of them.
The anterior cruciate ligament (ACL). The ACL is probably the best known of the knee ligaments and is extremely important in good knee health. The ACL keeps the tibia bone from being moved too far to the front of the knee in relative position to the femur bone. The ACL is one of four major ligaments inside the knee. It connects from the back and outside part of the femur bone to the front and inside part of the tibia bone.
The posterior cruciate ligament (PCL). Not to be confused with the Pacific Coast League of minor league baseball, the posterior cruciate ligament is the second of the four major ligaments in the knee. It connects the back intercondylar area of the tibia bone to the medial condyle of the femur. An exam called the posterior drawer test is used by doctors to detect injury to the PCL. During the test, the doctor will position himself sitting on the end of the patients foot with the knee turned 80 degrees. The doctor then jerks the tibia backwards. If there is excessive movement, a tear in the PCL is probable.
The Capsular Ligament. Also known as the joint capsules or articular capsules form a space for the bone joints to move in. Each capsule is made up of two layers - an outer layer made up of white, fibrous tissue, and an inner layer which secretes fluid.
The Ligamentum Patellae. The Patellar ligament is an anterior ligament and is a strong and flat band about 8 cm long and is attached to the kneecap and to the tibia. Its fibres stretch over the front of the kneecap with the tendon from the quadriceps.
The Medial Collateral Ligament. The MCL protects the side of the knee from being bent open from a force from the other side of the knee.
The Lateral Collateral Ligament. The LCL protects the knee from a bending force from inside the knee.
The Oblique Popliteal Ligament. The OBL is a broad, flat, fibrous band.
As you can see with all these different aspects to the knee there is a high possibility of things going wrong within the joint.
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