It is used to illustrate the necessity of chiropractic for kids. For some reason the idea of adjusting kids is off-putting to many adults. They picture me cracking delicate little spines, crunching tiny vertebra. They reason that kids don't, or shouldn't, have back pain, that this is an affliction of the middle-age, like arthritis and mom-jeans.
I'm not going to convince you that your children need to be adjusted regularly, I'm not convinced myself. If it ain't broke, don't fix it, right? But what do you do for the 8-year-old complaining of back pain? Or the 4-year-old who fell really hard on his bum at the park? Maybe your child has been having unrelenting digestive issues but has been cleared by every specialist in town... and you've heard that chiropractic just might help?? What then?
Then bring that child to the chiropractor. Find a doc who is comfortable working with little kids and little spines. Learn how gentle adjustments are on children, the force proportionate to the person. On tiny babies it is really more of a gentle, sustained pressure at a specific spot!
We ask a lot of kids. We encourage them to be active, making them vulnerable to the usual sports injuries, then sit them at a desk all day long like adults, predisposing them to postural problems. Yet we are shocked when little bodies hurt, and often reluctant to treat them. "Dylan shouldn't have back pain, he is only 10-years-old!" Can you imagine doing this with any other health problem? "Little Madison shouldn't have bronchitis, she is only 10-years-old!". Pain is just as real and important in kids as in adults, and they are no less deserving of treatment than we are.
One of the best things about treating kids is their lack of attachment to their aches and pains, combined with their short attention spans. Most of the time when I treat a child, only two or three visits are needed to 'resolve' the problem. They just... get better. When I ask at follow-up how their pain is, they often shrug and say 'fine', as if only 3 days ago they weren't complaining about the pain and asking to be let out of gym class. They just... get better.
As a chiropractor, I enjoy treating kids if and when it is appropriate. As a parent-to-be, I'll treat the spine of my spawn the same way - conservatively, if and when needed. I don't plan on ignoring their problems simply because they seem too young to be having them, and I don't plan to include back problems in their inheritance.
So back to that saying. As the twig is bent, so grows the tree. Injuries in childhood can become big problems in adulthood. Taking care of them early, nipping them in the bud as it were, will encourage good posture and spinal health.