Yeah they have computer assisted processing power, they make like 50 calculations a second about what you're doing and make corrections about what to do next. It's like if you are about to fall it will know that from the angles of trajectory the knee is in and it will instantly stiffen to try to help you regain your balance.

This is a great video to show the differences between the current tech out there and the C-Leg, the greatest innovation is you can WALK Down stairs, check it out:

http://www.youtube.com/watch?v=j0Y2o_ZybRs

Then there is this amazing video of a dude walking DOWN and UP Stairs, this is amazing, utterly amazing:

http://www.youtube.com/watch?v=RzKcTW7RDc8

This is one of a guy with TWO c-legs:

http://www.youtube.com/watch?v=rW-dOzYBFQM&NR=1