Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Arthritis ?
    ### Response:
    If you feel pain and stiffness in your body or have trouble moving around, you might have arthritis. Most kinds of arthritis cause pain and swelling in your joints. Joints are places where two bones meet, such as your elbow or knee. Over time, a swollen joint can become severely damaged.
    