We have the purple regions, our ligaments that connect bone to bone. We have these, the brown regions, which are the articular cartilage, the highland cartilage that we spoke about earlier, that reduces friction and that absorbs some of that shock. And we have this blue region shown. 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.