Knee Injuries and Disorders

Basic Anatomy of the Knee

The anterior aspect of the knee includes the kneecap, otherwise known as the patella. It is a sesamoid bone that is imbedded in an extensor tendon of the knee. The patella is triangular and is located in a groove formed by the femur; this protects the knee joint. In some instances, the patella may dislocate out of the groove from weakness of the muscles that form the extensor tendon of the knee. These muscles are located toward the interior aspect of the thigh, and are called the quadriceps. Nerve innervation is supplied to the quadriceps by the femoral nerve, which helps to straighten or extend the knee joint. The extensor tendon of the knee comes from the quadriceps and then attaches below the knee to the shin, or tibia. Attachment of the tendon occurs on the area of the tibia known as the tibialtuberosity.

The posterior aspect of the knee joint is referred to as the popliteal fossa. It is a diamond-shaped area that contains the tibial nerve, common peroneal nerve, and the popliteal blood vessels. These nerves and blood vessels supply the knee as well as the lower leg and foot. The posterior muscles of the thigh, the hamstrings, which bends or flexes the knee joint, forms this fossa. The hamstrings also prevent the tibia from sliding too far forward when the knee joint is in motion. Innervation to the hamstrings is supplied by the sciatic nerve.

The knee joint itself consists of an articulation between the femur, tibia, and patella. Between the femur and tibia is cartilage called meniscus, which acts as a cushion. The menisci also produce an increase in surface area contact between the femur and tibia. There are two menisci in the knee joint: the medial and the lateral. The medial is on the inside of the knee joint, and the lateral is on the outside. Both the medial and lateral meniscus attach to the medial portion of the tibia. The medial meniscus does not move while the lateral meniscus does. Also, between the knee joint are two support ligaments called the anterior and posterior cruciate ligaments. These ligaments prevent excessive forward and backward motion of the knee joint. They are named for where they originate on the tibia. The anterior cruciate ligament starts on the anterior aspect of the tibia and attaches to the posterior aspect of the femur. The posterior cruciate ligament originates on the posterior portion of the tibia and attaches to the anterior portion of the femur. These important ligaments maintain stability in the knee joint, and come into play when the femur tries to override the tibia.

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