my little escape artist

Calvin is my little escape artist. He somehow got past the 2 baby gates we have in this house and got to the top of the stairs yesterday w/o me even realizing it. When I discovered he was missing, I ran to the stairs as soon as I could, and found him at the top step, excited as can be! He was smiling and flapping his arms - obviously very proud of himself! I was so glad he didn't fall though. He can walk now! He's just 9 1/2 months, and can take 15-20 steps. Usually his attempts get him 5 or 6 steps but his longest was 15 or something like that. Violet fell down on the tile floor off the kitchen table chair the 2nd day we lived in this house. We winces in pain every time we pick her up from under the arms, we we have to avoid doing that. I even took her to the doctor because she seemed like it was bothering her so much, but it doesn't seem like anything is broken - he suspects a muscle spasm or a strain. Its a week later and it still hurts her.