What Part of Meadowsweet is Used Medicinally?

What part of the meadowsweet plant can I use in a tincture to ease my arthritis pain?

The above ground parts of meadowsweet (Filipendula ulmaria), the leaves and stems, are used medicinally in teas and alcoholic tinctures. You can make meadowsweet tea by steeping 1 teaspoon of the dried herb or 1 tablespoon of the fresh herb in a cup of boiling water for 15 minutes.