For a casual glance, Penguins, with their bulged belly and walking postures, appear to be not built with knees, whereas in reality, they do have knees hidden beneath their feathers. X-Rays taken of penguins establish beyond doubt the existence of their knees as part of the overall frame. But certain adaptations of their existence have made their walking a little harder for them.
Further, research has found that Penguins spend more energy for walking because of their body weight compared to other land animals, and that their life’s other adjustment needs make their movements in water easier. Actually, penguins are fast swimmers, and their prey as well as enemies subsist only under water. via neaq.org | via boredpanda