Stout with hairy to hairless foliage. Stem hollow, often purplish, shiny. Leaves pinnately compound. First pair of leaflets bends back sharply at stalk. Both common and species names (the latter meaning "having knee-like joints") refer to the uniquely bent leaf stalk. Egg- to lance-shaped leaflets 1–4 in. long, coarsely toothed. Petioles enlarged at base and sheathing stem. Umbel of 25–50 clusters of hairy flower heads with conspicuous bractlets on 2–7 in. stalks. White or pale pink flowers. Grows in streambanks, wet places, at low elevations.
- Rarity: Locally Common
- Flowering Time: Late Spring
- Life Cycle: Perennial
- Height: 3--8 feet
- Habitat: Meadow, Coastal, Bog/Fen/Wetland
- Found In: Olympic Np, West Gorge, Siskiyous, Columbia Basin, N Cascades Np, Mt. Rainier Np
- Native: Yes