dear cheryl,
I completely agree with elinwee.... a qualified paediatric physio will be able to assess your childs possibilities and discover if physio is necessary. Dr Touwen 1984 list on variation in motor miles gives a greater variation possibility than the AIMs =Alberta Infant Motor scale. Some kids take longer than others and cath up later.
dear elinwee,
if you are interested I could send you a paper about the current ideas on motordevelopment including his list. I would need you to send me your email adress so that I can send it to you.
mine is [email protected]

kind regards esther