(Source of images: Versus Arthritis Org)
Cartilage structure is practically a collagen fibres matrix, stuffed with proteoglycans. Proteoglycans are high molecular complexes, that attracts water, creating positive pressure within the cartilage, giving it the ability to withstand loading of pressure, for instance, when we stand, lifting weights, or doing any physical activity.
When wear-and-tear degeneration, aging process, and damage surpasses the rate of body's own ability or speed of repairing, the cartilages become thin. Under such conditions, movements of joints becomes less flexible, and often brings about discomfort and pain that affect mobility and quality of life.