An abnormal curve in the back has a specific medical name depending on the direction it curves. A sideways curve is called scoliosis. An exaggerated forward rounding of the upper back is called kyphosis (sometimes referred to as a “hunchback” curve). An excessive inward curve of the lower back is called lordosis, often described as “swayback.” Your spine naturally has gentle curves, so these terms apply only when a curve goes beyond the normal range.
The Three Types of Spinal Curvature
Your spine isn’t meant to be perfectly straight. Viewed from the side, it has a slight inward curve at the neck, a gentle outward curve in the upper back, and another inward curve in the lower back. These natural curves help you absorb shock and stay balanced. Problems arise when any of these curves becomes more pronounced than normal, or when the spine curves sideways in a way it shouldn’t.
Scoliosis is a lateral (side-to-side) curve of the spine measuring at least 10 degrees on an X-ray. Instead of running straight when viewed from behind, the spine forms a C-shape or S-shape. It most commonly appears in adolescents between ages 10 and 18, though it can develop in adults as well.
Kyphosis is an excessive forward rounding of the upper back. The normal curve in this region falls between 20 and 45 degrees. A curve greater than 50 degrees is classified as hyperkyphosis. It can give the appearance of hunching or slouching, even when you’re trying to stand up straight.
Lordosis is an exaggerated inward curve of the lower back. A typical lumbar curve ranges from 40 to 60 degrees. Anything beyond that pushes the pelvis forward and the belly outward, creating a pronounced arch that pulls your posture out of alignment.
Structural vs. Functional Curves
Not every curved back involves a permanent change to the spine. Doctors distinguish between two categories. A structural curve means the spine itself has grown or changed shape in a way that can’t be corrected simply by changing position. A functional curve is caused by something outside the spine, like a muscle imbalance, uneven leg length, or habitual poor posture. Functional curves often straighten out when you lie down or when the underlying cause is addressed. Structural curves do not.
This distinction matters because it changes how the curve is managed. A functional curve caused by a leg-length difference, for example, might improve with a shoe insert. A structural scoliosis curve that measures 30 degrees in a growing teenager requires a very different approach.
What Causes Spinal Curves to Develop
The most common form of scoliosis, called idiopathic scoliosis, has no identifiable cause. It tends to run in families and develops during the growth spurts of adolescence. Less commonly, scoliosis can result from birth defects in the spine, neuromuscular conditions like cerebral palsy, or connective tissue disorders.
In adults, spinal curvature often develops through a degenerative process. The cushioning discs between your vertebrae dry out and lose height over time. The small joints connecting the vertebrae (facet joints) develop arthritis, with cartilage wearing down until bone rubs against bone. These changes can happen unevenly on the left and right sides of the spine, gradually pulling it into a sideways curve. This is called degenerative scoliosis, and it typically affects people over 50.
Kyphosis has its own set of causes. In teenagers, a condition called Scheuermann’s disease causes several vertebrae to develop a wedge shape, locking the upper back into a rounded position. In older adults, kyphosis commonly results from osteoporosis, where weakened vertebrae compress and collapse. Lordosis can be driven by obesity, pregnancy, weak core muscles, or conditions that affect the hip joints.
Signs You Can See and Feel
Scoliosis often shows up as subtle asymmetry before it causes any pain. According to the Scoliosis Research Society, visible signs include one shoulder sitting higher than the other, one shoulder blade sticking out more prominently, uneven spacing between your arms and torso, one hip appearing higher or jutting out, and your head sitting slightly off-center over your pelvis. You might also notice that your waistline looks flattened on one side, or that your clothes hang unevenly.
A simple screening technique called the Adam’s Forward Bend Test can reveal scoliosis at home. Stand with your feet together, knees straight, and bend forward at the waist with your arms dangling. Have someone look at your back from behind. If one side of the rib cage appears higher than the other, creating a visible hump, that’s a strong indicator of a structural curve that warrants an X-ray.
Kyphosis is usually visible as a rounded upper back that persists even when you consciously try to straighten up. Lordosis is most noticeable from the side, where the lower back appears deeply arched and the belly pushes forward.
Degenerative curves in adults tend to come with symptoms that mild adolescent curves don’t. Back pain that worsens with standing or arching backward points to facet joint arthritis. Pain that gets worse when sitting or bending forward suggests disc degeneration. As the changes progress, the spinal canal can narrow and compress nearby nerves, causing pain, numbness, or weakness in the legs.
How Spinal Curves Are Treated
Treatment depends entirely on the type of curve, its severity, and whether you’re still growing. Many mild curves need nothing more than periodic monitoring with X-rays to make sure they aren’t progressing.
For adolescents with scoliosis, bracing is typically recommended once a curve reaches 25 degrees in a patient who is still growing. In younger children, bracing may start at curves as small as 20 degrees. The goal of a brace isn’t to straighten the spine, but to prevent the curve from getting worse during the remaining growth years. Braces are worn for a prescribed number of hours each day, often 16 to 23 hours, and are discontinued once growth is complete.
Surgery becomes the standard recommendation when a scoliosis curve reaches 50 degrees, because curves beyond that threshold tend to keep progressing even after growth stops. The most common procedure fuses the curved vertebrae together using metal rods and screws to hold the spine in a straighter position. Recovery typically involves several months of restricted activity, though most people return to normal daily life within six months to a year.
For kyphosis and lordosis, treatment often focuses on the underlying cause. Physical therapy to strengthen the muscles supporting the spine can improve both posture and pain. Osteoporosis treatment can help prevent further vertebral compression in older adults with kyphosis. In severe cases, surgical correction is an option, though it’s less commonly needed than with scoliosis.
Adult degenerative curves are managed primarily through pain control, physical therapy, and activity modification. Anti-inflammatory medications and targeted exercises to strengthen the core and back muscles are first-line approaches. Spinal injections can provide temporary relief when nerve compression is involved. Surgery for adult degenerative scoliosis is reserved for cases where nerve symptoms are severe or conservative treatment has failed over an extended period.