The synovial fluid is made by the synovium. This is
the tissue that surrounds the joint. The outer part of the synovium is
called the capsule. This is tough, gives the joint stability, and stops
the bones from moving 'out of joint'. Surrounding ligaments and muscles
also help to give support and stability to joints.
Who gets psoriatic arthritis?
About 1 in 10 people with psoriasis develop psoriatic arthritis. (About
2 in 100 people develop psoriasis at some stage in their life. See
separate leaflet called '
Psoriasis' for more details of psoriasis.)
In
most cases, the arthritis develops after the psoriasis - most commonly
within 10 years after the psoriasis first develops. However, in some
cases the arthritis develops much later. In a small number of cases the
arthritis develops first, sometimes months or even years before the
psoriasis develops. Men and women are equally affected.
Psoriasis
most commonly first occurs between the ages of 15 and 25, and psoriatic
arthritis most commonly develops between the ages of 25 and 50.
However, both psoriasis and psoriatic arthritis can occur at any age,
including in childhood.
Note: people with psoriasis also have
the same chance as everyone else of developing other types of arthritis
such as rheumatoid arthritis and osteoarthritis. Psoriatic arthritis is
different, and is a particular type of arthritis that occurs only in
some people with psoriasis.
What causes psoriatic arthritis?
The exact cause is not known. Inflammation develops in the synovium of
affected joints (the tissue that surrounds each joint) and sometimes in
other parts of the body such as tendons and ligaments. It is not clear
what triggers the inflammation. It seems that the immune system is
affected in some way which leads to inflammation. Genetic factors seem
to be important as psoriatic arthritis occurs more commonly in
relatives of affected people. However, it is not a straightforward
hereditary condition. It is thought that a virus or other factor in the
environment may trigger the immune system to cause the inflammation in
people who are genetically prone to it.
Which joints are affected in psoriatic arthritis?
Any joint can be affected. However, there are five
main patterns of this disease. Affected people tend to fall into one of
these patterns although many people overlap between two or more
patterns. The patterns are:
Asymmetrical oligoarticular arthritis
This
is a common pattern and tends to be the least severe. 'Oligo' means 'a
few'. In this pattern usually fewer than five joints are affected at
any time. A common situation is for one large joint to be affected (for
example a knee) plus a few small joints in the fingers or toes.
Symmetrical polyarthritis
This pattern is
also quite common. Symmetrical means that if a joint is affected on the
right side of the body (such as a right elbow) the same joint on the
left side is also often affected. Polyarthritis means that several
joints become inflamed, usually including several of the smaller joints
in the wrists and fingers.
Spondylitis with or without sacroiliitis
This
pattern occurs in about 1 in 20 cases. Spondylitis means inflammation
of the joints and discs of the spine. Sacroiliitis means inflammation
of the joint between the lower spine (sacrum) and the pelvis. Back pain
is the main symptom.
Distal interphalangeal joint predominant
This
is a rare pattern where the small joints closest to the nails (distal
interphalangeal joints) in the fingers and toes are mainly affected.
Arthritis mutilans
This is a rare pattern where a severe arthritis causes marked deformity to the fingers and toes.
What are the symptoms of psoriatic arthritis?
Joint symptoms
The common main symptoms are
pain and stiffness of affected joints. The stiffness is usually worse
first thing in the morning, or after you have been resting. The
inflammation causes swelling and redness around the affected joints.
Over time, in some cases, the inflammation can damage the joint. The
extent of joint damage can vary from case to case. On average, the
joint damage tends not to be as bad or as disabling as occurs with
rheumatoid arthritis. However, joint damage can cause significant
deformity and disability in some cases.
Inflammation around tendons
This is quite
common. It probably occurs because the tissue which covers tendons is
similar to the synovium around the joints. A common site is
inflammation of the tendons of the fingers. Affected fingers may become
swollen and 'sausage shaped' if there is inflammation in the finger
joints and overlying tendons at the same time. The achilles tendon is
another common site, especially where the tendon attaches to the bone.
Various other tendons around the body are sometimes affected.
The skin rash of psoriasis
See separate leaflet called 'Psoriasis' for details.
Other symptoms that may occur include:
- Inflammation of ligaments.
- Pitting of the nails (tiny depressions in the nail), and separation of the nail from the nailbed.
- Anaemia and tiredness.
- Inflammation in other parts of the body. Inflammation of the front
of the eyes (conjunctivitis) and/or of the iris around the pupil
(iritis) are the most common examples. Rarely, inflammation can develop
in other places such as the aorta (a main blood vessel) or lungs.
How is psoriatic arthritis diagnosed?
There is no test which clearly diagnoses early psoriatic arthritis.
When you first develop symptoms of arthritis it can be difficult for a
doctor to definitely confirm that you have psoriatic arthritis. This is
because there are many other causes of arthritis. However, if you have
developed psoriasis within the past few years, and then an arthritis
develops, there is a good chance that the diagnosis is psoriatic
arthritis.
In time, the pattern and course of the disease tends to become typical and a doctor may then be able to give a firm diagnosis.
Some
tests may be done such as blood tests and x-rays. These can help to
rule out other types of arthritis. For example, most people with
rheumatoid arthritis have an antibody in their blood called rheumatoid
factor. This does not usually occur in psoriatic arthritis. (This is
why psoriatic arthritis is described in medical textbooks as a
'sero-negative' type of arthritis - that is 'antibody-negative'.) Also,
the x-ray appearance of joints affected by psoriatic arthritis tends to
be different to that seen in rheumatoid arthritis and osteoarthritis.
How does psoriatic arthritis progress?
Once the disease is triggered, psoriatic arthritis is usually a chronic
relapsing condition. Chronic means that it is persistent. Relapsing
means that at times the disease flares-up (relapses), and at other
times it settles down. There is usually no apparent reason why the
inflammation may flare-up for a while, and then settle down.
The
amount of joint damage that may eventually develop can range from mild
to severe. At the outset of the disease it is difficult to predict for
an individual how badly the disease will progress. However, modern
drugs that are commonly used these days aim to suppress the
inflammation in the joints and prevent joint damage.
What are the treatments for psoriatic arthritis?
The main aims of treatment are:
- To reduce pain and stiffness in affected joints and tendons as much as possible.
- To prevent joint damage and deformity as much as possible.
- To minimise any disability caused by pain or joint damage.
Treatment aim 1 - to reduce pain and stiffness
During a flare-up of inflammation, if you rest the
affected joint(s) it helps to ease pain. Special wrist splints,
footwear, gentle massage, or applying heat may also help. Medication is
also helpful. Medicines which may be advised by your doctor to ease
pain and stiffness include the following:
Non-steroidal anti-inflammatory painkillers (NSAIDs)
These
are sometimes just called 'anti-inflammatories' and are good at easing
pain and stiffness. There are many types and brands. Each is slightly
different to the others, and side-effects may vary between brands. To
decide on the right brand to use, a doctor has to balance how powerful
the effect is against possible side-effects and other factors. Usually
one can be found to suit. However, it is not unusual to try two or more
brands before finding one that suits you best.
The leaflet
that comes with the tablets gives a full list of possible side-effects.
The most common side-effect is stomach pain (dyspepsia). An uncommon
but serious side-effect is bleeding from the stomach. Your doctor may
prescribe another medicine to 'protect the stomach' from these possible
problems. If you develop abdominal (stomach) pains, pass blood or black
stools, or vomit blood whilst taking anti-inflammatories, stop taking
the tablets and see a doctor urgently.
Note: it is thought that
some anti-inflammatories may make the rash of psoriasis worse in some
people. Tell your doctor if you think that your psoriasis has become
worse since starting an anti-inflammatory drug. An alternative
anti-inflammatory drug or a different type of painkiller may be an
option.
Painkillers
Paracetamol often helps. This
does not have any anti-inflammatory action but is useful for pain
relief in addition to, or instead of, an anti-inflammatory drug.
Codeine is another painkiller that is sometimes used.
Steroids
An injection of steroid directly
into a joint or inflamed tendon is sometimes used to treat a bad
flare-up in one particular joint or tendon. Steroids are good at
reducing inflammation.
Note: non-steroidal anti-inflammatory
painkillers, ordinary painkillers, and steroids ease the symptoms.
However, they do not alter the progression of the disease or prevent
joint damage. You do not need to take them if symptoms settle between
flare-ups.
Treatment aim 2 - to prevent joint damage as much as possible
Disease-modifying drugs
Disease-modifying
antirheumatic drugs (DMARDs) are commonly used as early as possible
after a diagnosis of psoriatic arthritis is made. They aim to suppress
inflammation and reduce the damaging effect of the disease on the
joints. They work by blocking the effects of chemicals involved in
causing joint inflammation. Sulfasalazine and methotrexate are the most
commonly used DMARDs for psoriatic arthritis, but there are others.
DMARDs
have no immediate effect on pains or inflammation. It can take up to
4-6 months before you notice any effect. Therefore, it is important to
keep taking a DMARD as prescribed, even if it does not seem to be
working at first. After starting a DMARD, many people continue to take
an anti-inflammatory drug for several weeks until the DMARD starts to
work. Once a DMARD is found to help, the dose of the anti-inflammatory
drug can be reduced or even stopped. It is then usual to take a DMARD
indefinitely.
Each DMARD has different possible side-effects. If
one does not suit, a different one may be fine. Some people try two or
three DMARDs before one is found to suit. (Some side-effects can be
serious. These are rare and include damage to the liver and blood
producing cells. Therefore, it is usual to have regular tests - usually
blood tests - whilst you take a DMARD. The tests look for some possible
side-effects before they become serious.)
Some DMARDs also have
a beneficial effect on reducing the psoriasis rash. For example,
methotrexate is an established treatment for psoriasis even in the
absence of arthritis.
Newer disease-modifying drugs
A new class of
drugs which have recently been developed are drugs that modify the
effect of TNF-alpha. The chemical TNF-alpha plays an important role in
causing inflammation in joints and skin. Blocking the effect of
TNF-alpha has been shown to reduce damage to joints, and reduce
symptoms. Drugs which modify or block the effect of TNF-alpha include:
etanercept, infliximab, adalimumab, and anakinra. They show promise but
their long-term benefits are still being evaluated. One problem with
these drugs is that they need to be given by injection. They are also
expensive. Recent guidelines state that one may be tried if there has
been little success when using standard DMARDs.
Treatment aim 3 - to minimise disability as much as possible
- As far as possible, try to keep active. The muscles around the
joints will become weak if they are not used. Regular exercise may also
help to reduce pain and improve joint function. Swimming is a good way
to exercise many muscles without straining joints too much. A
physiotherapist can advise on exercises to keep muscles around joints
as mobile and strong as possible. They may also advise on splints to
help rest a joint if needed.
- If such things as your grip or mobility become poor, an
occupational therapist may advise on adaptations to the home to make
daily tasks easier.
- If severe damage occurs to a joint, operations such as joint replacements are an option.
- Sometimes an operation is needed to fix a damaged tendon.
Other treatments
See the leaflet on psoriasis for details of treatments for the skin rash of psoriasis.
Some
people try complementary therapies such as special diets, bracelets,
acupuncture, etc, to help ease arthritis. There is little research
evidence to say how effective such treatments are for psoriatic
arthritis. In particular, beware of paying a lot of money to people who
make extravagant claims of success. For advice on the value of any
treatment it is best to consult a doctor, or contact one of the groups
below.
What is the outlook (prognosis) for people with psoriatic arthritis?
In many people with psoriatic arthritis the severity is mild to
moderate, the joint damage is not too bad, and there is no major
disability. In some people - perhaps up to 4-6 in 10 of untreated cases
- the disease can cause more marked symptoms with joint damage
developing over time and leading to disability.
However, the
figures quoted for prognosis are a bit confusing as treatment has
improved in recent years. Symptoms can often be well controlled with
medication. Because of the newer and better drugs, in particular the
newer disease modifying drugs, the outlook for a person who is
diagnosed with psoriatic arthritis these days is likely to be much
better than it used to be. Follow up studies of people being treated
with the newer drugs should give a clearer idea of prognosis over the
next few years.
Further information and help
PAPAA - The Psoriasis and Psoriatic Arthritis Alliance
PO Box 111, St Albans, Hertfordshire, AL2 3JQ
Tel: 0870 770 3212 Web: www.papaa.org
Arthritis Research Campaign - ARC
Copeman House, St Marys Court, St Marys Gate, Chesterfield, Derbyshire, S41 7TD.
Tel: 0870 850 5000
Web: www.arc.org.uk
Arthritis Care
18 Stephenson Way, London, NW1 2HD
Helpline: 0808 800 4050
Web:
www.arthritiscare.org.uk
References
© EMIS and PiP 2008 Updated: 13 Feb 2008
