Should I major in kinesiology before going on to get my doctorate in physical therapy?

Kinesiology, Human Anatomy or Exercise Science/Physiology are all great, traditional, options. However, you could major in anything (for instance ballet) as long as you complete the pre-requisites for your program. I know of a physical therapist who majored in dance, went to therapy school and now works exclusively with competitive level dancers in her private studio/clinic. So, you don't have to be pigeon holed.

Whatever you do, try to expose yourself to classes in Sports Medicine and Strength Training early in your collegiate career. They won't be prerequisites to any program that but they'll prepare you better for graduate school as well as open up internships and job opportunities while you're a student that others will not be qualified for.

Here's a list of DPT prerequisites taken from PTCAS.org (which is a system you'll probably use when applying for graduate school:
http://www.ptcas.org/uploadedFiles/PTCASorg/Directory/Prerequisites/PTCASCoursePreReqsSummary.pdf

Pick a major that you really enjoy. It can be great to balance all of the science classes you need to take as prerequisites with a major in the humanities or the arts. Majoring in something like kinesiology will give you some good background that will help you in PT school, but it isn't essential. Good luck!