The human knee, which is a diarthrodial joint, is a complex and important part of the human anatomy. This hinged joint enables the human being to perform various activities like sitting, walking and running. The movement of the knee joint may be compared to that of a door hinge. The knee joint is the largest joint in the human body.
The knee is made up of three bones: the patella (knee cap), the femur (thigh bone) and the tibia (shin bone). These bones are held together by ligaments (bands of tough fibers). Ligaments also facilitate active movement of the knee joint. Ligaments connect the thigh bone and the shin bone inside the knee.
The patella, which is a triangular shaped bone, provides much needed protection to this diarthrodial joint. It is located in front of the articulation of the thigh bone and the shin bone. The knee cap articulates primarily with the thigh bone. The femoropatellar articulation, the medial femorotibial articulation and the lateral femorotibial articulation are the three functional units of the human knee. The knee cap helps the human being to stand upright by preventing the legs from bending backwards.
The articular cartilage and the meniscal cartilage are the two types of cartilage present in the knee joint. The articular cartilage covers the ends of the bones and provides a sooth surface. Two pieces of meniscal cartilage are located between the femur and the tibia, one on each side of the knee joint. They act as shock absorbers while walking or running.
The synovium (or synovial membrane) is a lining of soft tissue inside the knee joint. It produces a lubricating fluid which facilitates easy movement of the knee. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are found in the intercondylar fossa of the femur. These ligaments control the movement of the tibia on the femur and allow flexion and extension of the knee. The lateral collateral ligament (LCL) and the medial collateral ligament (MCL) provide much needed support to the knee. Skin, muscles, tendons and ligaments outside the knee joint provide stability and facilitate motion.
It is very important to keep the knee joint healthy. This vital part of the human body is vulnerable to injuries, as it supports the weight of the human body. Knee problems are usually caused by medical conditions like arthritis and trauma. Persistent pain or swelling in the knee joint should be brought to the attention of a certified physician without delay, to avoid further complications.
Further Reading: Hyperextended Knee Symptoms and Treatment