Do penguins have knees?

Though their legs are quite short, penguins do, in fact, have knees! The New England Aquarium has published a blog post all about this question. If you look at a penguin's skeleton, you can see that their legs are composed of a femur, tibia, fibula, and a knee joint. Because a living penguin has a fluffy undercoat for warmth and a slick topcoat of feathers for water resistance, it can be tricky to tell what bones or muscles might be underneath that hydrodynamic shape. The femurs and knees of a penguin are positioned towards the back and almost entirely inside the main body cavity. (Some scientists think this is part of the reason they waddle on land.) Though this limits some motion we might associate with having knees, penguins can still hop, walk, and perform a kicking motion to propel themselves through water.