Ankylosing spondylitis is a painful condition, and for many people, pain is the symptom that drives them to seek a diagnosis in the first place. The pain is inflammatory in nature, meaning it behaves differently from a typical back injury. It tends to be worst during rest and at night, improves with movement, and can persist for months or years if untreated. Nearly 60% of people with the condition experience sleep disturbances tied to their pain levels.
Where the Pain Starts
The earliest pain almost always begins at the sacroiliac joints, the two joints where the base of your spine meets your pelvis. Inflammation at these joints, called sacroiliitis, produces a deep ache in the buttocks that can radiate into the thigh or lower back. This is the hallmark first symptom. The pain is often hard to pin down because it doesn’t feel like a pulled muscle or a sharp injury. It’s more of a dull, persistent soreness that builds gradually over weeks or months.
From there, inflammation can spread upward through the spine. The lower back and hips are the most commonly affected areas, but the condition can also involve the mid-back, rib cage, shoulders, heels, and other joints where tendons and ligaments attach to bone. These attachment points, called entheses, are particularly vulnerable because they bear high mechanical stress from everyday movement, standing, and walking.
Why It Hurts More at Rest
This is what sets ankylosing spondylitis apart from most other causes of back pain. A herniated disc or muscle strain typically feels worse when you move and better when you rest. Ankylosing spondylitis works in reverse. The pain worsens during periods of inactivity, which is why many people notice it most in the middle of the night or after sitting for a long time. Getting up and moving around generally brings relief, at least partially.
Morning stiffness is one of the defining features. Stiffness lasting more than 30 minutes after waking is a clinical marker used to help distinguish inflammatory back pain from other types. In diagnostic criteria, this morning stiffness combined with improvement during exercise and no relief from rest forms a recognizable pattern. If your back pain fits this description and you’re under 40, it’s a pattern worth investigating.
Night Pain and Sleep Disruption
Nighttime is often the hardest part of the day. A study of 314 people with ankylosing spondylitis found that 58.6% were at high risk for sleep disturbances, and 35.4% qualified as poor sleepers. The difference between those who slept well and those who didn’t came down largely to nocturnal pain. Poor sleepers rated their nighttime pain nearly twice as high as good sleepers on a standard pain scale.
The most common consequence was daytime dysfunction, reported by 57.6% of patients. That means fatigue, difficulty concentrating, and reduced productivity during the day, all flowing from disrupted sleep. Nocturnal pain, depression, and anxiety were the three strongest predictors of sleep problems, and they tend to reinforce each other. Poor sleep increases pain sensitivity, which worsens sleep further, creating a cycle that’s difficult to break without treatment.
How Pain Changes Over Time
Ankylosing spondylitis follows a progression, though the speed varies enormously from person to person. In the early stages, pain comes from active inflammation at the sacroiliac joints and spine. The body responds to this chronic inflammation with a cycle of tissue erosion followed by new bone formation, essentially trying to repair damage by laying down extra calcium.
Over years or decades, this cycle can cause sections of the spine to fuse together. Fused vertebrae no longer move independently, which creates a different kind of pain and stiffness. Even the sacroiliac joints, which normally move only a few millimeters, can fuse completely. This limits your ability to bend forward, backward, and side to side. At this stage, pain may come less from active inflammation and more from the structural rigidity of the spine, loss of normal posture, and strain on the joints and muscles that compensate for lost mobility.
Not everyone progresses to fusion. Early diagnosis and modern treatment have made severe spinal fusion less common than it once was.
Pain Beyond the Spine
While the spine and sacroiliac joints get the most attention, ankylosing spondylitis can produce pain in other areas. Hip involvement is common and can be particularly limiting because it affects walking, climbing stairs, and sitting comfortably. Shoulder pain, heel pain (from inflammation where the Achilles tendon attaches to the bone), and rib cage stiffness that makes deep breathing uncomfortable are all possible.
Some people also experience inflammation in the eyes, gut, or skin as part of the broader disease process. Eye inflammation, called uveitis, causes sudden eye pain, redness, and light sensitivity. These extra-spinal symptoms don’t happen to everyone, but they’re common enough that doctors consider them part of the overall picture.
How Well Treatment Controls Pain
The good news is that pain from ankylosing spondylitis responds well to treatment in the majority of people. Anti-inflammatory medications are the first step and provide meaningful relief for many. For those who need more, biologic therapies that target the specific inflammatory molecules driving the disease have transformed outcomes.
Clinical trials of these biologics consistently show strong pain reduction. Across multiple studies, roughly 60 to 75% of patients achieved at least a 20% improvement in their symptoms within 12 to 16 weeks, compared to only 20 to 30% of patients taking a placebo. More impressive, about 40 to 50% hit a higher bar of 40% improvement or greater. Some smaller studies found that over 90% of participants experienced at least a 20% reduction in their overall pain assessment, with more than half reaching 70% reduction.
Exercise is equally important and is considered a core part of managing the condition. Regular movement, particularly stretching, swimming, and strength training, helps maintain spinal flexibility, reduces stiffness, and directly alleviates pain. This aligns with the nature of the disease itself: movement calms the inflammation, while inactivity feeds it.
Pain in ankylosing spondylitis is real, often severe, and sometimes invisible to others because the damage is internal. But it is also highly treatable. Most people who get an accurate diagnosis and consistent treatment are able to manage their pain well enough to maintain active, full lives.