Ankylosing spondylitis typically starts as a deep, dull ache in the lower back and buttocks that comes on gradually over weeks or months. Unlike a pulled muscle or herniated disc, this pain gets worse with rest and better with movement. Most people first notice it in their mid-20s, and it often takes about six years from the first symptoms to get a diagnosis.
How the Pain Starts
The earliest sensation is usually stiffness and pain centered where the base of the spine meets the pelvis, at the sacroiliac joints. It doesn’t arrive suddenly the way a muscle strain does. Instead, it creeps in over several weeks, often so gradually that you might dismiss it as sleeping in a bad position or overdoing it at the gym. The pain tends to alternate sides or feel like it spans the entire lower back and hips.
What makes this pain distinctive is its relationship to activity. Mechanical back pain from a sprain or disc problem hurts more when you move and eases when you sit or lie down. Ankylosing spondylitis works in reverse. Sitting still for a long meeting, a long car ride, or a night in bed makes the stiffness worse. Getting up and moving around gradually loosens things. Morning stiffness is one of the hallmark experiences, and for many people it’s the most frustrating part of the day. Your back feels locked in place when you wake up, and it can take anywhere from 30 minutes to well over an hour of gentle movement before you feel functional.
What Nights Are Like
Sleep disruption is one of the most common complaints. The inflammatory process that drives the disease tends to intensify during the second half of the night, so many people find themselves waking at 2 or 3 a.m. with deep, aching back pain that won’t let them fall back asleep. In one study, 88% of patients with spondyloarthropathy reported difficulty staying asleep. The issue isn’t usually falling asleep initially. It’s the mid-sleep awakening, that restless period where no position feels comfortable and the stiffness builds until you’re forced to get up and walk around.
Pain Beyond the Spine
Ankylosing spondylitis doesn’t stay confined to the lower back. One of the more confusing symptoms, especially early on, is pain at the points where tendons and ligaments attach to bone. This is called enthesitis, and it shows up in predictable places: the back of the heel where the Achilles tendon connects, under the heel at the sole of the foot, the front of the shin just below the knee, and where the ribs meet the breastbone. The sensation at these spots is a localized, tender soreness that can feel like a sports injury you don’t remember getting.
When enthesitis affects the rib joints, it creates a specific and sometimes alarming symptom: chest pain that worsens with deep breathing. Taking a full breath feels restricted, like wearing a too-tight vest. Over time, the chest wall can lose flexibility, which makes aerobic exercise feel harder than it should. People with AS have significantly reduced chest expansion compared to the general population, and the sensation during a deep breath is often described as tightness or pressure rather than sharp pain.
The Fatigue
If you asked people with ankylosing spondylitis what surprised them most about the condition, many would say the fatigue. About 45% of people with inflammatory rheumatic diseases experience clinically significant fatigue, and in AS it’s closely tied to pain levels. This isn’t the kind of tiredness that a good night’s sleep fixes. People describe it as overwhelming, something that permeates every aspect of life and resists the usual strategies for managing it. It’s the kind of exhaustion that makes concentrating at work difficult, that cuts social plans short, that turns routine errands into something you have to psych yourself up for.
Research consistently shows that worsening pain and fatigue together reduce work productivity, physical functioning, and the ability to engage in daily activities. The fatigue feeds the pain, the pain disrupts sleep, and poor sleep deepens the fatigue. That cycle is often what finally pushes people to seek a diagnosis.
Eye Symptoms
Roughly a quarter to a third of people with ankylosing spondylitis will experience at least one episode of acute eye inflammation, called uveitis. It typically hits one eye at a time and comes on fast. The eye becomes red, painful, and extremely sensitive to light. Vision may blur. It feels like something is in your eye that you can’t blink away, and bright lights or even a normally lit room can become genuinely uncomfortable. These episodes need prompt treatment to prevent lasting damage, and they often recur.
What Progresses Over Time
In its early stages, ankylosing spondylitis is primarily a pain and stiffness disease. Over years or decades, the inflammation can trigger new bone growth along the spine. Ligaments and the outer layers of spinal discs gradually calcify, and individual vertebrae can fuse together. On an X-ray, this looks like a single rigid column sometimes called “bamboo spine.”
What this feels like from the inside is a progressive loss of range of motion. Turning your head to check a blind spot while driving becomes difficult. Bending forward to tie your shoes requires new strategies. Some people develop a fixed forward curve in the upper back that shifts their center of gravity and affects balance. The spine also becomes more brittle as it fuses, meaning that even minor falls or jolts can cause fractures that wouldn’t happen in a healthy spine. People with advanced fusion describe their back as feeling like a single rigid rod rather than a flexible chain of bones.
Not everyone progresses to this stage. Modern treatments can significantly slow or halt the fusion process, especially when started earlier. But the gradual stiffening is something many people notice well before it shows up on imaging, as a slow shrinking of what their body can comfortably do.
Why It Takes So Long to Diagnose
The median time from first back pain to diagnosis is about six years, and for women it’s closer to seven. Symptoms start in the mid-20s on average, an age when back pain is usually attributed to posture, stress, or physical activity. The pain builds slowly, there’s no single dramatic event that triggers a doctor visit, and standard X-rays can look normal for years before visible changes appear. Many people cycle through physical therapists, chiropractors, and general practitioners before someone connects the pattern: young onset, gradual worsening, morning stiffness, improvement with exercise, worsening with rest, and pain that wakes you in the second half of the night.
If that pattern sounds familiar, the combination of those features is what distinguishes inflammatory back pain from the mechanical kind. Any one symptom alone is common and nonspecific. Together, they paint a picture that points toward a condition worth investigating.