Joints
Joints are the place where bones are connected. In the joints that enable different parts of your body to move - for example, your shoulder, elbow, hips and knees - the bones are tipped with smooth cartilage. This is made slippery by an oily fluid so that the bones can slide over each other. In other joints, particularly ones in your skull, neighbouring bones are firmly locked together. This ensure that these parts of the skeleton stay in exactly the right position.The hip joint is shaped so that the thighbone can swivel in many different directions. In the skull, zigzag joints keep bones locked together so they cannot move. This protects the brain.