Could “cracking your back” be the solution for backaches and headaches? The answer is yes, claim advocates of spinal manipulation.

Spinal manipulation, also called spinal manipulative therapy or manual therapy, combines moving and jolting joints, massage, exercise, and physical therapy. It’s designed to relieve pressure on joints, reduce inflammation, and improve nerve function. It’s often used to treat back, neck, shoulder, and headache pain. Chiropractors use it to treat other disorders too, such as menstrual pain and sinus problems.

Today, spinal manipulation is used in both Western and traditional Asian medicine. In North America, it’s usually performed by chiropractors, osteopathic physicians, and physical and occupational therapists.

Forms of manipulative therapy have been used for thousands of years in many parts of the world, including Indonesia, Asia, India, Russia, and Norway. Writings from China in 2700 B.C. and from Greece in 1500 B.C. mention manipulating the spine and legs to ease back pain. The ancient Greek physician Hippocrates, who is viewed as the founder of medicine as a rational science, describes manipulative techniques in his writings.

Spinal manipulation gained and lost favor with physicians many times through the mid-1800s. It was viewed as a practice of folk healers, called bonesetters, whose successes were attributed to luck.

Modern spinal manipulation traces its roots to nineteenth century America. Disillusioned by the deaths of his three children, a doctor named Andrew Taylor Still developed the theory that diseases were caused by displaced bones and muscles interfering with the body’s circulatory system. He turned to spinal manipulation as a non-drug, holistic method of correcting body imbalances and restoring health. In doing so, he became the father of modern osteopathy.

Daniel David Palmer developed the theory that diseases were caused by spinal misalignments, or subluxations, that block the transmission of the body’s own healing power through the nervous system. His theories would eventually form the basis of chiropractic medicine.

There are over 100 types of spinal adjustments used by chiropractors worldwide. Some use force and twisting (spinal manipulation), while others techniques are more gentle (spinal mobilization). In addition, practitioners use ice and heat therapy, electric stimulation, traction devices that stretch the spine, and ultrasound for deep tissue heating. Most procedures are done on a padded, adjustable table. Parts of the table can be dropped as an adjustment is being done, adding different forces to the movement.

In spinal manipulation, the practitioner uses their hands to apply a controlled, sudden force to a specific joint. Patients often hear popping noises, like when you crack your knuckles.

In spinal mobilization, practitioners use less forceful thrusts and more stretching. They will sometimes use an “activator,” which is a small metal tool that applies force directly to one vertebra.

Besides chiropractors, osteopaths and some physical therapists use spinal adjustments.

Measuring the effectiveness of spinal manipulation is difficult because it doesn’t lend itself to traditional studies. A 2007 study found spinal manipulation to be moderately effective in easing chronic low back pain lasting four or more weeks. Researchers said it was also slightly to moderately effective in easing acute low back pain that lasted less than four weeks. Another study showed that six weeks of mobilization treatments helped treat neck pain in almost 70 percent of participants.

Spinal adjustment is usually safe when it’s performed by someone trained and licensed to deliver the care. Serious complications are rare, but can include herniated disks, compressed nerves, and even a stroke after neck manipulation.

Some people should avoid spinal manipulation or adjustments, including people who have severe osteoporosis, high stroke risk, spinal cancer, or an unstable spine. People who experience numbness, tingling, or loss of strength in an arm or leg should also avoid these treatments.

Because of the danger of injury and the lack of proven long-term benefits, spinal manipulation remains a controversial therapy for any disorders not involving joints or muscles.