Читать книгу Arthritis For Dummies - Barry Fox - Страница 43

The ultimate cause of primary osteoarthritis remains a mystery. Although scientists aren’t sure why, the collagen mesh of the cartilage becomes scrambled; it weakens and can’t hold its structure. The proteoglycans, once so cozily intertwined in the collagen mesh, suddenly find themselves evicted from their secure homes. As they float off into the joint fluid, they take their water-retaining abilities with them. The cartilage is left high and dry; it thins and may even crack. At the same time, the newly freed proteoglycans draw excess fluid into the joint capsule, causing swelling. (Unfortunately, this fluid can’t get back into the cartilage, where it’s desperately needed. It’s something like dying of thirst in the middle of the ocean.)

Although no one is absolutely certain what causes primary osteoarthritis, here are a few theories:

 The chondrocytes become too efficient at breaking down the collagen and proteoglycan molecules. In healthy cartilage, the amount of breaking down enzymes is equal to the amount of building up enzymes. An overabundance of destructive enzymes leads to weakened collagen and a lack of proteoglycans.

 The chondrocytes go wild and start making too many proteoglycan and collagen molecules. The opposite of the previous condition, these chondrocytes are too good at making new cartilage components. The excess proteoglycan and collagen molecules, in turn, pull extra fluid into the joint, flooding it and washing away most of the chondrocytes. The cartilage, then, is left bereft of cartilage-producing molecules.