Lumbar lordosis refers to the natural inward curve of your lower back. It's a key element of posture, whether good or bad. When the angle of this curve is too extreme, often called a sway back, it can cause a lot of problems—including misalignment and pain. The same goes for too shallow an angle. However, determining a "normal" angle is more difficult than you might expect.
That technical name for that inward curve is the lordotic curve. "Lumbar" is the name for a region of your lower spine.
There is no normal range for lumbar lordosis. Angles vary wildly from one person to another, as each person's lordosis is based the relationship between their spine and their pelvis, a measurement called pelvic incidence. Lumbar lordosis should match the pelvic incidence +/- 10 degrees.
Measuring Your Lordotic Curve
An X-ray is the first step doctors take to measure the lordotic curve. Even this can be problematic, though. A 2014 study published in Spine Journal found that positioning during testing and the number of vertebrae included in the measurement may contribute to skewed results.1
Adding to the confusion are characteristics you bring to the X-ray table. According to the study authors, numerous factors can make it difficult, if not impossible, to determine your lumbar angle. These complicating factors include:1
Body mass index (a height-to-weight ratio used to determine if you're underweight, average weight, overweight or obese)
Interpreting the X-Ray
Doctors use several systems to interpret the lumbar X-rays and determine the degree of lumbar lordosis. They include:
Determining the lumbar curve's Cobb angle from an X-ray taken in profile
Using what's called the centroid, tangential radiologic assessment of lumbar lordosis method (TRALL)
Using the Harrison posterior tangent line-drawing methods
A 2001 study found that determining the Cobb angle is usually the most accurate for the low back.2
What is the Cobb Angle?
Why Measure Lumbar Lordosis?
If coming up with normal values for a very normal phenomenon such as the lumbar curve is so hard, you may wonder why it's done at all.
Despite the problems, the information is still useful—especially when taken into consideration with pelvic incidence. For example, when doing a spinal fusion surgery, spine surgeons will measure the lumbar lordosis and pelvic incidence to ensure that the spine is being put into an alignment that allows the patient to stand upright.
Researchers from the 2014 study mentioned above found an association between the lumbar lordosis angle and spine conditions such as spondylolysis and isthmic spondylolisthesis, so the measurement may be used to determine risk. It may also influence the treatment decisions you and your doctor make if you have one or both of these back conditions.1
A 2017 systematic review and meta-analysis identified a strong relationship between low back pain and the loss of the lumbar lordosis angle—which is sometimes called "flat back"—especially when the decreased lumbar angle was associated with disc degeneration or herniated discs.3
What Does It Mean for You?
For those of us who wish to be proactive about addressing our posture issues, this lack of decisiveness about "normal" for the all-important low back curve can be frustrating. To that end, here are a few things to keep in mind.
In and of itself, a lumbar lordosis does not present a problem. Once it becomes excessive, though, it can make your back muscles tighten and cause pain. It also may increase your risk of facet joint pain or spinal arthritis.
Conversely, if your lumbar lordosis decreases, perhaps because you have a habit of sitting with a slouch every day at work, you may increase your risk for a disc injury.
While it is possible to be born with an excessive or minimal lumbar curve, this is extremely rare. Most of the time, posture habits and conditioning are at the root of a lumbar curve angle that doesn't match your pelvic incidence.
A Word From Verywell
Based on everything we know, it's likely that the best way to get your low back curve in line is with a core exercise program. No matter what your number is at the moment, strong core muscles can keep your back curve within the optimal range for you, or, if it's outside that range, get it back in.