Ankylosing spondylitis (AS) is a chronic, inflammatory condition that particularly affects the spine. But it can also affect several other joints, such as the hips, knees and chest wall. It can also affects areas where tendons attach to bone, such as where the Achilles’ tendon attaches to the heel or where the tendons at the elbow get inflamed. The severity and pattern of joint involvement varies from person to person.
Ankylosing spondylitis often begins at a young age (from the teens to the third decade of life) and is more common in men (about two to three times more common than in women). AS can also affect children, called juvenile ankylosing spondylitis, and more commonly so in boys than girls.
"Ankylosing" refers to the tendency of the bones of the spine to fuse, due to inflammation of the ligaments that attach one vertebral body to another and to bony overgrowth. (See Fig. 1)
"Spondylitis" refers specifically to the inflammatory process ("itis") of the spine. As a result of this inflammation, a person feels stiffness and pain in the back, a gradual loss of mobility, and in the more severe cases, a complete loss of motion of the lower back. The neck (cervical spine) often has a similar inflammatory process and can likewise progressively lose motion.
It is very important to get an early diagnosis for ankylosing spondylitis, since treatment is needed even for mild and early cases. All patients with AS need to begin a physical therapy regimen as soon as possible, and a significant number need strong medications to quiet the inflammation and keep them functional.
Genetics play a large role in this condition; over 90% of those with ankylosing spondylitis have a particular genetic marker that can be found on their white blood cells, called HLA-B27. This means that a number of people with AS will have a family history of the condition, although it may be much more painful and involve more areas of the body in one family member than another. Many people with AS will not be able to identify anyone else in their family with the condition, however, since only about 20% of those with the HLA-B27 gene will experience inflammatory conditions such as AS.
Although the HLA-B27 genetic marker appears to play a role in over 90% of cases of ankylosing spondylitis, this marker does not appear to be the only cause, as 80% of people with this genetic marker never develop an inflammatory disease. Some environmental factor (and likely there is more than one), which has yet not been determined, clearly plays a role in determining which people with this genetic makeup end up with AS.
People with the HLA-B27 genetic marker can develop other types of inflammatory conditions other than ankylosing spondylitis, such as eye inflammation with no arthritis. As noted above, having this genetic marker does not by itself mean you have ankylosing spondylitis or any other inflammatory condition. Diagnosing AS is really a matter of medical history, physical exam, and X-ray or other imaging studies, more than any specific blood test.
The most common symptom of ankylosing spondylitis is low back pain and/or neck pain, morning stiffness and limited motion that is improved by exercise and unrelieved by periods of rest. Joint pain in the hips, shoulders, knees, chest wall, or other areas is the next most common symptom.
Eye inflammation (uveitis) can occur in this condition, and regular ophthalmology checkups are important, since eye dramaticge can occur even before a person notices any symptoms. Heart and lung problems can also be associated with AS, but are fortunately less common.
Symptoms of ankylosing spondylitis vary from patient to patient, but they most commonly begin with the onset of low back pain and stiffness that is especially noticeable in the morning hours and after long periods of rest. This pain is usually relieved by physical activity and improves by the end of the day. Some patients experience similar pain in the buttocks, hips, chest wall, upper back, and neck. If left untreated, the ankylosing process can result in a "hunchback" appearance.
Patients are also prone to an onset of arthritis in the large joints and elsewhere, and can – in some cases – experience heel pain related to Achilles tendonitis, lung problems (as a result of lung scarring and spinal inflammation, limiting chest expansion), aortitis (inflammation of the aortic valve and the large artery – the aorta – coming from the left side of the heart), and uveitis, which can lead to visual loss.
Early diagnosis is very important with ankylosing spondylitis. The difficulty of diagnosing ankylosing spondylitis lies in differentiating its symptoms from those of other forms of low back pain. In order to make this distinction, a combination of diagnostic measures are required, including a physical exam, imaging studies, and laboratory tests.
Imaging studies include X-ray and, if necessary for more detailed evaluation, CT exams or MRI scanning. Lab tests are employed to detect signs of an inflammatory process (for example, the sedimentation rate may be elevated as a sign of inflammation in AS). A blood test for the HLA-B27 gene marker can be helpful, but the diagnosis is made by a combination of history, exam, lab and imaging studies.
As with most other inflammatory types of arthritis, there is not yet a cure for AS. Fortunately, however, medication and physical therapy treatment can usually make a dramatic difference in a person’s symptoms and function. For certain types of joint problems, local steroid injections can help. In rare cases, surgery is involved in special problems with the spine.
It’s essential for all ankylosing spondylitis patients to engage in physical therapy and home exercise progras, and to strive for proper maintenance of posture to help maintain maximum possible flexibility. AS stiffens the spine and tends to position the head to be held forward and the lower back to remain in a flexed position. Stretching and exercise regimens aim to oppose these tendencies and to increase flexibility.
Since the lungs can be affected in AS – both by scarring due to inflammation and by decreased chest expansion due to chest wall inflammation – breathing exercises are important. This can help patients with AS maintain their exercise tolerance. It is also important for this reason for AS patients to stay away from smoking.
Medications can be tremendously helpful in relieving pain, restoring mobility, and stopping or slowing disease progression.
While nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin, naproxen, and celecoxib haven’t been consistently shown to affect the tendency of the spine to fuse, they work to reduce inflammation, stiffness, and the resulting pain in many patients with AS. For some people with milder spondylitis, NSAIDs may be all the treatment they need, along with physical therapy.
There has been excellent evidence that anti-TNF agents (a group of medications within the category of biologic medications) can provide marked functional improvement, and these are used in many patients with more serious disease. These anti-TNF agents – including infliximab, etanercept, adalimumab, golimumab and certolizumab – improve mobility while alleviating pain. The anti-TNF medications are given either by self-injection or intravenously.
Another group of biologic medications approved by the FDA for ankylosing spondylitis block a chemical called IL-17. The two approved such medications are secukinumab and ixekizumab. These are self-injected medications.
Other medications under study for ankylosing spondylitis include the group of oral medications called Jak inhibitors, such as tofacitinib and upadicitinib.
For patients with AS and arthritis of the hip or knee, for example, local steroid injections can help with pain and stiffness.
Surgery is usually considered when AS has progressed to a point at which the patient’s mobility is severely impaired due to chronic, debilitating pain or a painful deformity. The great majority of patients with AS never need surgery. For those who do, several procedures are available.
The nature of the surgery will depend on the degree of deformity, whether or not the bony changes are causing any pressure on nerves, and the stability of the spine. The procedures will generally involve an osteotomy, which refers to the removal of some of the bone and realignment of the spine; instrumentation and fusion are generally used to allow the bone to heal in a stable position. Also, some people with ankylosing spondylitis will have severe enough hip arthritis that they need a hip replacement, but this is uncommon.
The type of surgery will depend upon the specific case and the judgment of the surgeon – and again, surgery is rare in ankylosing spondylitis.
As is true for all types of inflammatory arthritis, ankylosing spondylitis progresses differently on a patient-by-patient basis, and symptoms will vary accordingly. In some patients, the hardening of the spine occurs at a faster rate, while others will experience only slight inflammation and pain, and little loss of function.
Again, in common with many other types of inflammatory arthritis, ankylosing spondylitis is not presently curable, but very effective treatments exist. Non-steroidal anti-inflammatory agents (such as indomethacin or naproxen) can be extremely helpful, and pain killers without anti-inflammatory properties (such as acetaminophen) can also help. The anti-TNF medications clearly often provide dramatic improvements in function and may prove effective in halting the disease in the long term. Anti-IL-17 medications are also of major help. Surgery is an occasional option for those with advanced, debilitating forms of the disease.
Regardless of the medications used in the individual case, the importance of exercise and physical therapy cannot be overstated.
The outlook for patients with ankylosing spondylitis is much better today than it was 15 years ago. It is very important for AS to be diagnosed as early as possible, before the spine has a chance to fuse. If a person with AS is faithful to their exercise and physical therapy program, and works with their rheumatologist to develop a medication regimen that is right for them, their chances of a highly functional, long-term outcome are excellent.