Now the blue region is basically a cavity known as the synovial cavity. And inside this synovial cavity we basically contain our synovial fluid. And this synovial fluid does not only lubricate and provide nutrients to our cartilage but it also contains macrophages cells that basically engulf different type of harmful bacteria that can harm our cartilage. So basically this joint, the synovial joint consists of our ligaments, it consists of this synovial fluid that basically nourishes this cartilage. And it also consists of this highland cartilage that absorbs the shot and also basically reduces the friction between our bones so the bones don't actually rub against one another. So the synovial joint consists of a cavity that contains our synovial fluid which acts to nourish our cartilage found nearby.