The knee acts like a hinge and a shock absorber when you walk, run, jump, kick, or climb. Ligaments, tendons, and muscles give the knee stability and hold it together. Rubbery tissue called cartilage covers and cushions the ends of the bones that make up the knee. These bones include the femur, or thighbone, the tibia, or shinbone, and the patella, or knee cap. Osteoarthritis of the knee means the cartilage in the joint has broken down because of excessive wear due to obesity, injuries, or overuse. It is also called degenerative arthritis and degenerative joint disease, or DJD. When knee cartilage is rough, frayed or worn away, the bones can grind against each other, which can make the knee joint irritated, painful, and swollen.
