Its always a dream for humanoid robot builders to replicate human running style. Although legged running robots have been built in the past, most of them don't have knees. The one's with knees can't run very fast; A good example is the Honda Asimo which has knees but it can only walk steadily and run upto 6 Km/hr, although I would like to say its one of the best humanoids ever built.
A robot developed at the University of Michigan lab can run like a human with features that represents the height, agility and efficiency of humans for a two-legged machine. With a peak pace of 6.8 miles per hour or 10.94Km/hr, MABEL is believed to be the world's fastest bipedal robot with knees.
Mabel was a project that was built back in 2008 with collaborating members which include Jonathan Hurst, a doctoral student at the Robotics Institute at Carnegie Mellon University, Jessy Grizzle a professor at U-Mich. Doctoral students, Koushil Sreenath who is in the U-M Department of Electrical Engineering and Computer Science. Hae-Won Park is in the U-M Department of Mechanical Engineering the later have contributed to developing the Algorithm and model for the robot. Since then the team has been progressively improving the feedback algorithms that enables the robot to keep its balance while reacting to its environment in real time.