How does ankylosing spondylitis affect the bones?

Published Mar 18, 2024 • By Claudia Lima

Ankylosing spondylitis affects the joints of the spine, hips or lower back. It manifests itself through inflammation of the enthesis, the part of the bone where tendons, ligaments and capsules are inserted. In some cases, AS can lead to joint damage and bone deformities, particularly in the spinal column.

How exactly can ankylosing spondylitis affect the bones?

Read our article to find out!

How does ankylosing spondylitis affect the bones?

What are the symptoms of ankylosing spondylitis?  

Ankylosing spondylitis is a chronic inflammation of the joints. It affects the spine and the sacroiliac joints in the pelvis. On a day-to-day basis, this causes joint pain, chronic fatigue and joint stiffness

These symptoms can prevent the patient from carrying out simple everyday tasks.

The evolution of ankylosing spondylitis varies according to the intensity of inflammation and the degree of joint damage.

If left untreated or if treated ineffectively, ankylosing spondylitis can lead to disabling complications. This disease can progressively and permanently block the joints of the lower back, by fusing the pelvic bones with the sacrum, or fusing several vertebrae together. 

In the most severe cases, the spinal column can be fused into a single bone. These fusions cause stiffness and characteristic deformities of the spine.

How does ankylosing spondylitis affect the bones?  

In some patients, ankylosing spondylitis becomes increasingly severe, with more and more frequent flare-ups

Possible complications include: 

Ankylosis of the spine 

Inflammation spreads to an increasing number of joints, and can extend throughout the spinal column. The affected areas can become progressively stiff until they become totally ankylotic, leading to severe deformity and discomfort

Ankylosis of the thoracic cage 

Stiffness of the spine can restrict the ability to expand the chest which leads to breathing difficulties.

In addition, if the joints that connect the ribs to the spine are inflamed, the pain may limit thoracic expansion needed for deep breathing.


Excessive and abnormal curvature of the spine, with the back arched and the neck bent forward, called kyphosis, is common in untreated patients.

Hypercyphosis develops when the person loses lumbar lordosis and adopts a fixed position, bent forward, with impaired respiratory function and an inability to lie flat.

Bilateral coxitis

BIlateral coxitis is damage to the coxofemoral joint. It is a marker of the severity of the disease, as it affects the functional prognosis: both hips may be blocked and walking made impossible.

Fractures of the vertebrae 

These fractures occur even after a mild trauma and affect the vertebrae of the neck. They are attributed to both bone demineralization and spinal rigidity.

Cauda Equina syndrome 

It is caused by the compression of the nerves at the bottom of the spinal cord, which causes pain or loss of feeling in the lower part of the body, as well as loss of mobility in the legs or toes, constipation, urinary incontinence, etc.


Patients with ankylosing spondylitis have an increased risk of developing osteoporosis due to chronic inflammation and prolonged use of steroid medication. Weakened bones can also increase the risk of fractures

If patients are properly monitored, they will benefit from appropriate treatment to alleviate their symptoms and prevent complications.

How can these complications be treated?  

The frequency of medical follow-up is tailored to each patient. Nevertheless, patients with ankylosing spondylitis should benefit from regular medical appointments to detect early signs of bone complications.

X-ray examinations and bone density tests may be recommended.

At each medical appointment, the doctor should assess:

  • The progression of the disease and how the patient feels about it: the degree of fatigue and pain intensity, damage to joints and ligaments or tendons, etc. ;
  • Functional difficulties, i.e. the impact of spondyloarthritis on the patient's daily activities;
  • Mobility at lumbar, thoracic and cervical level, noting down the results and using them as benchmarks for subsequent examinations.

Early treatment helps control inflammation, thereby reducing the risk of subsequent impact of the disease on the patient's bone health.

If the bones become affected, the patient should be cared for by a specialized medical care team, which should include orthopedic surgeons and chiropodists. The orthopedic surgeon is responsible for treating pain and joint stiffness by carrying out surgical procedures (joint replacement, correction of deformities). The podiatrist may prescribe the use of special equipment designed to reduce pain and prevent deformity (such as orthopedic insoles).

How can you reduce or prevent the impact of ankylosing spondylitis on your bones?   

There are a number of simple things that you can do to improve your quality of life if you suffer with ankylosing spondylitis. 

Here are just a few of them: 

  • Taking a complete rest in the event of a painful flare-up
  • Taking the painkillers prescribed by your doctor to avoid getting into bad postures, 
  • Having a regular physical activity, especially stretching and strengthening exercises, or other sports that do not traumatize your spine: swimming on your back, walking, Tai chi, etc,
  • Carrying out daily stretching exercises to keep your spine straight, keep your vertebrae mobile and maintain a good range of movement, 
  • Eating a well-balanced diet, rich in calcium and vitamin D, which are essential for bone health, 
  • Maintaining good back posture when standing or sitting, and avoiding incorrect posture, 
  • Sleeping on a firm mattress that lies as flat as possible, 
  • Learning to manage stress, which can aggravate your symptoms and encourage inflammation. Relaxation techniques such as meditation and yoga can be beneficial. 

Another support tool for ankylosing spondylitis is therapeutic patient education, the aim of which is to enable patients to better cope with certain situations and to learn how to monitor the progress of their disease, so that they can seek help quickly in the event of complications. It gives them a better understanding of their disease and of the correct use of treatments, and enables them to learn how to protect their joints and relieve joint pain, adapt their lifestyle and make those around them aware of the significant impact of the disease.

Ankylosing spondylitis can lead to significant complications affecting the bones, but early and appropriate treatment can reduce these risks. Patients should be aware of the signs of these complications and work closely with their medical care team to prevent and treat these problems effectively, in order to minimize their impact on patients' daily lives.

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avatar Claudia Lima

Author: Claudia Lima, Health Writer

Claudia is a content creator at Carenity, specializing in health writing.

Claudia holds a master's degree in Entrepreneurship and an Executive MBA in Sales and Marketing Management. She is specialized in... >> Learn more


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