When a person has constant stress on their joints, like the knee or the ankle, or suffers a physical injury from a fall or while exercising, the joints start to suffer a deterioration of cartilage.  Everyone needs cartilage around their joints to disperse the pressure on the  joint and protect it and the bones inside it, from deteriorating or suffering damage.  As we get older, the cartilage gets less resilient and can’t absorb the stress of bodies  activity.  This is the on-set period for some types of arthritis.  Doctors have recently discovered that instead of using anti-inflammatory drugs to fight the pain and stiffness of joints, lubricating the joints with oral glucosamine,  can slowly hydrate the cartilage  to give it elasticity back, and hydrate the drying cartilage.