My niece looks like she has bowed knees!?

Hey, never used this thing before but yeah, I'm just wondering to ask a question to see if anyone knows of any problem alike. My four-year-old niece has two main problems and shes had them for about 6 months now. Like any normal child she has nightmares, but its every night and she starts crying for about 10 minutes but shes of course still asleep. And the second problem which is a bit worrying is her knees. For a four year old she is quite tall and very skinny, which is like her mom, but since she was really really little, her kneecaps have always stood out. Like they seem swollen and oddly shaped, like she has bowed knees but we never forced her to walk and they stick out more as shes getting older. Some days they will stick out to the side and shes slower than other children. My sisters gone to a children's hospital and the doctor there couldn't say what it was either. He recognized that she was slower than other children and takes her a long time to get up and sit down. But this wa about two months ago and the doctor said they would get back in contact with her so she could see a specialist in the leg area. Don't worry if you don't know what the problem is either, but if you have any suggestions would be good. Were not too worried atm, because shes young and is still growing! Thanks, sorry for the long question!