Dietary Supplement Undenatured Collagen Joint Comfort Cartilage is the connective tissue that covers the ends of your bones to form a smooth, shock-absorbing surface for your joints. Years of stress from our own immune system can wear away cartilage and limit joint flexibility. UC-II, or undenatured type II collagen, when taken orally helps support a healthy inflammatory response, immune function, and increased joint flexibility and mobility.