Remember the joints? They have a special protective lining called synovium and a liquid called synovial fluid that helps joints move smoothly.

Sometimes, the immune system—our body’s army—gets confused and sends the wrong commands, attacking the joints by mistake.

It is when juvenile idiopathic arthritis happens. This makes the synovium produce too much fluid, turning the joints swollen, stiff, and painful.

It is like having a little balloon filled with too much water inside the joint, making it hard and sore to move.