What causes backache at a very small age?

In past ,neither children nor teenagers didn't cause from backache.Now days children starting from 11 years has backache.why does it happen? what precautions should a child take to prevent the backache at a very small age? Even teenagers causes from backache.what precautions should teenagers take to prevent... show more In past ,neither children nor teenagers didn't cause from backache.Now days children starting from 11 years has backache.why does it happen?
what precautions should a child take to prevent the backache at a very small age?
Even teenagers causes from backache.what precautions should teenagers take to prevent backache?
Thanks a lot for those who have answered----
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