Has anyone had a child that learned to walk on their knees?

My granddaughter learned to walk on her knees. She got around like this for months. She finally stood up next to a wall when she was 18 months old and just took off walking everywhere. She hardly ever crawled. When she was old enough to set up and she wanted to watch anyone walk thru the house, she would just use her feet to spin on her butt in the direction she wanted to look. We would give her toys and show her how to play with them but she would just sit there with them in her hands.

My granddaughter is now almost 4 years old but acts more like she's barely 3. She answers "yes" to almost all questions. We can barely have a conversation with her. She is alert to what's going on around her, and does play with her cousins but it's mostly imitating what they're doing.

I might also mention she was tongue-tied when she was born and she also has two different ears. They're not deformed but they don't look alike. She seems very intelligent at times. She walks on her tip toes alot, covers her ears if there's loud noise or the conversation gets to noisy (she might even cry sometimes) & she's a picky eater. She has no fear of strangers but can be scared easily.

Many in our family know there is something not normal but can't figure it out. My son mentioned our concerns to her doctor but he said all kids develop differently. In all of my web searches this site comes closer to what she does than any other. If anyone recognizes any of this please reply.