Developmental Milestone Source Healthy Children Category Movement Expected age 48 No additional description of this milestone is available. Represented Developmental Observations IDOB#5265009 Walks down stairs without support, alternating feet IDOB#5264008 Walks down stairs without support, putting both feet on each step IDOB#5262007 Walks up stairs without support, alternating feet IDOB#5261000 Walks up stairs without support, putting both feet on each step