Using the leaves with their little prickly needles is best. A leaf freshly removed from the plant and simply applied all around the knee. Not severely crushing the leaf, simply folding it up in the hand or fisting it and then applying the leaf on the entire circumference of the knee. No need for water, no need for bandages. Apply it and forget about it and throw the used leaf in the compost. The little needles of the plant are the secret of comfrey, not the green juice.