Talk to Pediatric Orthopedic Surgeon on Child Walked Late & Has Weak Legs While Running

My child is 4 years old. He started walking late and initially walked on his toes. Now he walks normally, but when he walks or runs, it’s clearly visible that he lacks strength in his legs. Also, he doesn’t eat meat, eggs, or similar protein-rich foods. Please advise what could be the reason and what steps we should take.