Does the length of your thigh bones determine your height?

Yes, Along with other inherited factors. Take a look at a row of people sitting down. If they are all adults of the same sex, they all look about the same height. But once they stand up, you can clearly see that some people are a few inches taller than others! That's because the length of their torsos (neck to top of leg) are all about the same. Once they stand up, the length of their thighs makes the difference in height. The femur, or thigh bone, makes up 2/8 of a person's total height.