The knee is the largest joint in the body. A healthy knee moves easily, allowing you to walk, turn, and do many other activities without pain.

Every day, your knees must support your full body weight. Cartilage is the “shock absorber” of your knee joints, but over a lifetime it can start to wear away. This "wear and tear" arthritis (osteoarthritis) is the most common cause of knee pain.

Without your cartilage protecting your knees, your bones grind against each other, which causes you pain: pain that you can feel climbing stairs, working in the garden, or just trying to sit down. It may even keep you up at night.