An arthrosis of the knee joint, known in medical terms as Gonarthrose, is understood to mean all signs of wear in the knee joint, that lead to a progressive destruction of the joint cartilage assisted by the joint structures. Apart from the cartilage surfaces, the joint forming bone, the joint capsule as well as the musculature can collaborate. Arthrosis is understood to mean signs of wear initiated by a disproportion of the joint load and the actual loading capacity. A limit is set by the joint cartilage, which covers the bony joint surfaces as a sliding surface and which is truly worn down. Primarily this is an absolutely normal part of getting older.

Apart from these primary arthroses due to the process of getting older, so-called secondary arthroses, which are reducible to a wrong load on the knee joint, like for example knock knees or bandy legs, overweight or poorly healed bone fractures. Reasons for arthroses can also be injuries of the knee joint, tearings of the menisci, ruptures of the anterior and posterior cruciate ligament as well as accidental cartilage fractures. Moreover metabolic disorders like diabetes mellitus, gout as well as rheumatic diseases or bacterial or viral infections can lead to a knee joint arthrosis.

Severity codes of the arthrosis

In an internationally respected classification of arthrosis according to Kellgren and Lawrence 4 degrees (stadiums) of severity for arthrosis in X-ray images were defined:

Stadium

I                      Low subchondral sclerosing. No osteophytes. No joint gap narrowing.

II                     Low joint gap narrowing. Beginning formation of osteophytes.

                       Indicated irregularity of the joint surface.

III                    Distinctive formation of osteophytes. Joint gap narrowing. Clear

                       irregularity of the joint surface.

IV                    Distinctive joint narrowing up to complete destruction. Deformation/

                       Necrosis of the joint partners.