after the age of 30 a variety of age relate changes have been report in cartilage these is a gross alteration from a bluish translucent structure to a yellowith opague one surface cracking fraying and fibrillation.the earliest stages of degeneration of cartilage probably results from a progressive reduction in the ability of the chondroblasts to secrete adequate amounts of glycoprotein.proper lubrication of the joint during movement will become more difficult as the hyaluronic acid secretion is reduce greater friction and heat will be generated during movement.a reduction in the secretion of chondroitin sulfate will result in a reduce ability of matrix to retain fluid and the movement of material into and out of the cartilage will be hampered.