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Ankylosing spondylitis belongs to a group of disorders called the spondyloarthropathies, a group which also includes psoriatic arthritis, reactive arthritis and arthritis related to inflammatory bowel disease. All these conditions are linked by the genetics of a gene on white blood cells called HLA B27 and by the presence of enthesitis, inflammation at the points where ligaments and tendons insert into bone. This can lead to fibrosis at these sites and then bone formation, causing joint fusion (ankylosis) in some cases.

Ankylosing spondylitis belongs to a group of disorders called the spondyloarthropathies, a group which also includes psoriatic arthritis, reactive arthritis and arthritis related to inflammatory bowel disease. All these conditions are linked by the genetics of a gene on white blood cells called HLA B27 and by the presence of enthesitis, inflammation at the points where ligaments and tendons insert into bone. This can lead to fibrosis at these sites and then bone formation, causing joint fusion (ankylosis) in some cases.

The commonest spondyloarthropathy is Ankylosing spondylitis, which occurs as a reflection of the occurrence of the HLA B27 gene in the population. The gene occurs much less commonly near the equator and much more commonly in northern latitudes, and this is also the pattern with the development of AS. White race people are more commonly affected with around 0.1 to 1.0 percent overall, varying with latitude. Only 1 or 2 people of a hundred with the HLA B27 gene actually develop AS, but if they have a close relative who has the condition the likelihood rises to 15 to 20%.

AS occurs more often in males, with a 3:1 ratio, but females may suffer much milder disease or have minor symptoms which are not diagnosed. AS is a disease of young men, with most presenting before they are 40 years old, and 10-20% presenting with the disease before they are 16. On average people get the symptoms of the disease around 25 years old and are rarely diagnosed when over 50 years of age. The condition is often missed initially as it presents as low back pain so it is important to take a proper history. A useful question is "how does your back feel when you wake up" and AS patients will all say "very stiff".

Ankylosing spondylitis has similarities but distinct differences from the much more common low back pain:

Morning stiffness in the lumbar spine, lasting at least 30 minutes or longer Exercise improves the back pain and stiffness Rest worsens the pain and stiffness Pain is usually worse in the second half of the night, after a time of rest Peripheral joints are affected in 30 to 50% of patients Tiredness is common AS has systemic affects from its inflammatory nature which can include feeling unwell, fever and loss of weight.

Physiotherapy examination of the spine in an AS patient usually uncovers significantly reduced ranges of spinal movement from normal, with perhaps a reduced lumbar lordosis and an increased thoracic curve. Neck movements may also be limited in later stages and a reduction in chest expansion noted due to rib joint involvement. Peripheral symptoms occur in around a third of patients and the physio will palpate the tender areas, searching for evidence of enthesitis in the insertions of the Achilles tendon and plantar ligament of the foot. These are areas of high mechanical stress and commonly affected.

Postural analysis of the AS patient is the first thing a physiotherapist notes after the subjective examination, recording spinal abnormalities, flexed knees, rounded shoulders or poking head posture. The ranges of movement of the cervical, thoracic and lumbar spine are measured and a battery of standard measures taken which allows assessment of the disease progression. The hips or other peripheral joints may be affected and these need to be measured also, with the physio likely testing out sites where the enthesis is likely to be painful and inflamed. If the disease is active then the patient may also have joint effusions and may appear unwell, be sweating and not have slept well.

Physiotherapists will concentrate on treating the inflamed areas first such as the areas where the ligaments insert into the bone, using insoles, cold, ultrasound and stretching techniques. Routine spinal range of motion exercises are taught to patients with an emphasis on getting to end ranges, concentrating initially on the anti-gravity muscles such as thoracic and lumbar extensors. Neck rotation and retractions and thoracic rotations are also important functional movements not to lose. Patients should rest themselves in good postures such as prone or supine with only one pillow, to avoid accentuating the typical spinal deformities. Treatment for AS in a hydrotherapy pool is beneficial and soothing and patient education important so they keep up their programme.