Manipulating the spine can help people with lower back pain — but it doesn't work for everyone, according to a new study.

Spinal manipulation, or applying force to the joints of the spine, is a technique commonly used by chiropractors and physical therapists, according to the National Center for Complementary and Integrative Health. However, there is conflicting evidence about whether the treatment actually helps people, the researchers wrote in their study.

In the new study, the researchers found that spinal manipulation therapy (SMT) provided relief for some patients with lower back pain, but not for others.  [5 Surprising Facts About Pain]

"The big finding is that both sides have been right all along," said Greg Kawchuk, a professor of rehabilitation medicine at the University of Alberta and co-author of the study. It's not a matter of whether the treatment works or doesn't work, but rather, figuring out the best way to care for each patient, he said.

In the study, 32 people with lower back pain received two spinal manipulation treatments over the course of a week. They told researchers how much pain they felt, and the researchers also looked at objective measures of improvement, including measurements of muscle activity, disc hydration and spinal stiffness. A control group of 16 people underwent similar physical examinations, but did not receive treatment. A third group, of 59 people who did not have back pain, was also included, to provide another comparison.

Among the participants who underwent the spinal manipulation treatments, 15 said that they felt better, and the researchers found that their physical measurements all improved as well, Kawchuk told Live Science. For example, their measurements of disc hydration and spinal stiffness were nearing those of the people without any back pain at the end of the study, he said.

The people who said they did not feel any better did not have those physical changes, Kawchuk said.

It's unclear why the treatment worked for some patients but not others, but one idea is that the people who felt that the treatment worked have different spinal characteristics, Kawchuk said. The researchers need to do a much larger study to see whether that may be the case, he added.

The new study "is the beginning of an attempt to understand why some patients respond to SMT and others do not," said Dr. Allyson Shrikhande, a rehabilitation physician at Lenox Hill Hospital in New York City, who was not involved with the study.

Previous studies have looked at how SMT can affect people's pain levels and degree of disability, but they didn't include the physical measurements, Shrikhande told Live Science in an email.

She added that it would have also been beneficial if the researchers had examined how the treatment affected patient's hamstring flexibility, because this can significantly affect people's bodies.

For the people who were not helped by the spinal manipulation treatments, it's not all bad news.

Future research will be aimed at figuring out what does work for these people, such as massage or surgery, Kawchuk said. The ultimate goal is to be able to match patients with the treatments that work best for them, he said.

"Back pain is not one problem — it's a group of problems," so there won't be one treatment that works for everyone, Kawchuk said.

The study was published on Aug. 31 in the journal Spine.

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