Which structure protects the ends of bones at joints and aids in smooth movement?

The structure that protects the ends of bones at joints and aids in smooth movement is cartilage. Cartilage serves as a cushion between bones, covering the surfaces where they articulate with one another. This protective layer minimizes friction and allows for smoother movements during joint actions, such as bending and twisting. Additionally, cartilage absorbs shock and distributes weight across the joint, which helps prevent damage to the underlying bone during physical activity.

In contrast, tendons connect muscles to bones, helping to transmit forces that produce movement, but they do not directly contribute to the smoothness of joint movement. Ligaments connect bone to bone and provide stability to the joint but are not involved in reducing friction at the joint surface. The joint capsule is a tough, fibrous structure that encases the joint, providing stability and protection, but it does not have the same smooth, gliding properties as cartilage that facilitate movement.