Can you as a doctor really pridict how tall a patients gonna be?

No: But based on parental height we can give you a pretty good guess which will be fairly accurate a fair percentage of the time. In other words, the apple doesn't fall far from the tree, and two five foot parents are unlikely to produce a seven foot kid.

Predicting height: Yes. One must assume a child is growing normally. We need current height and an x-ray of their left hand and wrist called a bone age radiograph. Using these we can predict final height.

We do routinely: The growth charts you may see at the office are part of our usual well kid evaluation. We take the average of both parents height, add 2.5 inches for males and subtract 2.5 inches for a female. The resulting number is usually within an inch of final height. If you have taller parents and plot on the shorter part of the growth chart, we are more likely to check you out for a growth problem.