Milestones

Hello! My baby girl will be 13 months next month. She is still not interested in walking, not even crawling. When put into a crawl position, she will go into belly time mode and push herself forward with her right leg and drags her left leg. She barely even wants to stand (supported) on her own. She has a hard time bending at her knees when we assist her in walking or assist her in standing up (Her legs are so stiff). But when sitting or laying, her knees bend fine. We are currently in PT, but I feel like it is not working. I know each baby is different, but my first two were walking by their 1st bday. What age did your baby walk?