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Walking upright

The knee joint - anatomy and function

The knee is the joint that comes under the most pressure from daily activities. It connects the two largest bones in the human body. Since it lacks a mostly bony aposition it can only function if the active stabilizers, the muscles, and the passive stabilizers, the ligaments, menisci and joint capsule, complement each other perfectly.

In addition to the muscles of the thigh and shin, the main stabilizers are the anterior and posterior cruciate ligaments (ACL and PCL), which run through the centre of the joint. The anterior cruciate ligament stabilizes the joint against dislocation to the front and the posterior cruciate ligament prevents dislocations to the back. The stabilizers to the side are the medial and lateral collateral ligaments. The inner and outer menisci act as a "movable cup" and provide for a perfect gliding motion of the thigh bone (femur) against the shin bone (tibia). This gliding motion only works well if the cartilage cover of the two bones is intact and the joint produces enough lubrication fluid.

Powerful shocks, as they happen in accidents, can lead to injuries of the joint capsule and ligaments, of the inner or outer menisci, or of the cartilage.

Pain in younger patients is usually due to impairment of the ligaments or menisci, whereas in older patients it is more often due to cartilage wear (arthritis). 
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