Pain and Stiffness
Ankylosing spondylitis (AS) is a type of chronic inflammatory arthritis that most often begins in late adolescence or early adulthood, although in some cases it can begin in childhood or later adulthood. It is more common in men, although it occurs in both sexes. The symptoms and progression of the disease vary between different individuals.1,2
Does AS cause pain and stiffness?
AS causes severe, chronic pain and stiffness in the joints affected, which are most often the spine and hips. Often the earliest symptoms are felt in the sacroiliac (SI) joints, which are located where the hip bones (pelvic bones) meet the base of the spine. Some people also have pain and inflammation in other joints, like the shoulders, ribs, hands or feet. As the condition progresses, it can cause joints in the spine to become fixed or fused, which can lead to a loss of mobility and/or a curved posture (called kyphosis).1,2
The pain and stiffness caused by AS generally begins gradually, developing slowly over several weeks or month. The pain of AS is diffuse (spread over an area, rather than a specific point), dull, and may be constant and severe, although some people have pain that comes and goes. While the pain may begin on one side of the body, it can progress to both sides or may radiate to nearby areas. The stiffness of AS is generally worse in the morning, after a night's sleep, as well as worse after periods of inactivity. The stiffness and pain often improve with movement and activity or a warm shower. Both the pain and stiffness of AS are chronic, lasting for more than 3 months.3,4
Where does pain and stiffness occur with AS?
AS most commonly affects the spine. While each person with AS can have differences in their symptoms, AS frequently begins in the SI joints and progresses up the spine. The involvement of the joints between the vertebrae in the spine can cause a reduction in the range of motion a person has, making it difficult to twist or rotate. If AS affects the joints between the ribs and the spine or the ribs and the breastbone, it can be difficult to fully expand the chest cavity, causing chest pain or difficulty taking deep breaths.5
In addition to the spine, some people with AS experience joint pain and stiffness in other joints of the body. Approximately 30% of people with AS experience hip or shoulder involvement. When AS affects the hips, it may cause referred pain, a confusing symptom that causes pain in the front of the thigh or in the knees. About 30% of people with AS experience pain and stiffness in their heels, which can make it difficult to walk. More rarely, people with AS are affected in their jaw, which can make it difficult to open the mouth and may impair eating, or in their hands and fingers, which can make it challenging to do many daily tasks.5
How is inflammatory back pain different than mechanical back pain?
Inflammatory back pain, such as that caused by inflammatory conditions like AS, is different than mechanical back pain. Mechanical back pain is defined as pain that is due to the joints, discs, vertebrae, or soft tissue. Mechanical back pain commonly only lasts for about 4-6 weeks. Acute mechanical back pain is a common problem, with many people experiencing this type of back pain at some point in their lives.6
Mechanical back pain may be caused by trauma or strenuous activity, but most of the time the exact cause is unknown. Fortunately, most people recover from mechanical back pain with rest, over-the-counter pain relievers like non-steroidal anti-inflammatory drugs (NSAIDs), and alternately applying heat and ice.6
In contrast, inflammatory back pain caused by AS is chronic, lasting more than 3 months, and is worse with inactivity.3 A doctor can determine whether back pain is due to mechanical back pain or inflammatory back pain.