Chiropractors treat patients with health problems of the musculoskeletal system, which is made up of bones, muscles, ligaments, and tendons. They use spinal manipulation and other techniques to treat patients' ailments, such as back or neck pain. Many believe that misalignments of the spinal joints interfere with a person's nervous system and can result in lower resistance to disease and many different conditions of diminished health. Some chiropractors use additional procedures, such as acupuncture, massage therapy, and ultrasound. They also may apply supports, such as straps, tape, braces, or shoe inserts, to treat patients and alleviate pain. In addition to operating a general chiropractic practice, some chiropractors specialize in sports injuries, neurology, orthopedics, pediatrics, nutrition, internal disorders, or diagnostic imaging. Becoming a chiropractor requires earning a Doctor of Chiropractic degree and getting a state license. Doctor of Chiropractic programs take 4 years to complete and require 3 years of previous undergraduate college education for admission.