The human spine is composed of bones (vertebrae) that are stacked on top of each other and cushioned by rubbery pads that lie between them, called “spinal disks” or intervertebral disks. The spinal disks are roughly a quarter of an inch thick, with an elastic, fluid-filled core. They help prevent bone-on-bone friction and also increase the spine’s shock-absorption and flexibility. However, when subject to stress, the material inside the spinal disks can swell, bulging out from between the vertebrae and pressing against the surrounding nerves.1 This “herniated disk” is a common cause of lower back pain, and flexion distraction manipulation is one way to treat it.2
Flexion distraction manipulation is a chiropractic therapy in which the patient lies face-down on a mobile table, which gently stretches the spine while the practitioner massages key areas of the back. (“Flexion” refers to bending the body in such a way that brings joints closer together, and “distraction” refers to the pressure put on the body.) This creates a negative pressure that pulls the disk back between the vertebrae. It also prevents the tough, circular exterior of the spinal disk, the annulus fibrosus, from becoming distorted, which can cause pain. Since its invention in the 1960s by James Cox, flexion distraction has been the subject of various case studies and anecdotal reports, which have helped characterize and clarify its therapeutic benefits.2
For example, a 2019 study published in the Journal of Physical Therapy Science by Oh et al. examined the clinical outcomes of 30 female patients who visited a South Korean orthopedic clinic with symptoms consistent with herniated intervertebral disks. The researchers administered flexion distraction and another, similar chiropractic therapy (the drop technique) to two groups of 15 herniated disk patients. The control group received spinal decompression — non-chiropractic therapy that uses a specialized medical device instead of manual therapy. The researchers found that the patients’ straight leg raising angle and intervertebral disk height significantly improved in both groups, but that there was no significant difference in the increase when comparing the groups — in other words, the treatments were equally effective.3
The effectiveness of flexion distraction for patients with herniated disks has been repeatedly demonstrated. Kwon et al., cited by Oh, also found improved straight leg raising angles after application of flexion distraction.3 A study by Gudavalli et al. of cadaveric spines found that spinal disk space increased by approximately 3 mm and the angle of the intervertebral disk by around 6 degrees in the lumbar vertebrae of cadavers.4 In the study by Oh et al., the disk space increased by an average of 1.3 mm.3 Gay et al. found in another cadaveric study that the technique decreased the pressure within the intervertebral disk by 65 percent.5
Ultimately, patients may choose flexion distraction manipulation over another type of therapy based on their specific ailment. Choi et al. examined the effects of flexion distraction manipulation in 30 patients with lumbar spinal stenosis (narrowing of the spinal canal, which can be due to disk bulging), finding that while both pain and disability decreased in both groups, the decreases were more significant in the flexion distraction group in an intergroup comparison.6 This could support the use of flexion distraction for spinal stenosis over other therapies — spinal decompression therapy, for example, is not recommended for patients with spinal stenosis. Similarly, spinal decompression therapy is not recommended for spondylolisthesis and ankylosing spondylitis, but flexion distraction may be advisable.7
While flexion distraction manipulation remains a popular treatment option for a variety of conditions, including those involving disk pain, scientific studies evaluating its efficacy remain limited. A 2005 literature review of flexion distraction manipulation identified 30 articles on the topic, most of which were case reports or studies with small sample sizes. The article concluded that further investigation is needed “to establish the efficacy and safety of distraction manipulation and to explore biomechanical, neurological, and biochemical events that may be altered by this treatment.”8
1. Wheeler T. Understanding basic information about spinal disk problems. Webmd.com. Published 2019. https://www.webmd.com/pain-management/understanding-spinal-disk-problems-basic-information
2. Merckling J. Flexion distraction to the rescue for chronic back pain. Mercklingdc.com. Published 2018. https://mercklingdc.com/2018/10/29/flexion-distraction-to-the-rescue-for-chronic-back-pain/
3. Oh H, Choi S, Lee S, Choi J, Lee K. Effects of the flexion-distraction technique and drop technique on straight leg raising angle and intervertebral disc height of patients with an intervertebral disc herniation. J Phys Ther Sci. 2019;31(8):666-669.
4. Gudavalli MR, Cambron JA, McGregor M, et al. A randomized clinical trial and subgroup analysis to compare flexion-distraction with active exercise for chronic low back pain. Eur Spine J. 2006;15(7):1070-1082.
5. Gay RE, Ilharreborde B, Zhao KD, Berglund LJ, Bronfort G, An K-N. Stress in lumbar intervertebral discs during distraction: a cadaveric study. Spine J. 2008;8(6):982-990.
6. Choi J, Lee S, Jeon C. Effects of flexion-distraction manipulation therapy on pain and disability in patients with lumbar spinal stenosis. J Phys Ther Sci. 2015;27(6):1937-1939.
7. Spinal decompression vs chiropractic flexion-distraction technique. Evergreenclinic.ca. Published September 26, 2020. https://evergreenclinic.ca/difference-between-chiropractic-flexion-disctraction-technique-and-spinal-decompression/
Gay RE, Bronfort G, Evans RL. Distraction manipulation of the lumbar spine: a review of the literature. J Manipulative Physiol Ther. 2005;28(4):266-273.