Acute CPP crystal arthritis

Acute calcium pyrophosphate (CPP) crystal arthritis is a condition that can cause pain and swelling in your joints. 'Acute' means that the symptoms develop quite suddenly.

Calcium crystals occur naturally in the body. For example, they help to make our teeth and bones strong. However, some people can have these crystals in other parts of the body, for example in the cartilage that covers the ends of the bones where they meet in a joint. 

Many people have calcium crystals in their cartilage for years without them causing any problems. But sometimes the crystals shake loose from the cartilage (this is called shedding) and move into the space between the bones, called the joint cavity. When this happens it can cause painful inflammation and swelling as the hard, sharp crystals rub against softer tissues.

Acute CPP crystal arthritis was sometimes called pseudo-gout, meaning false gout, because the symptoms are similar to gout. However, gout is caused by crystals of a waste product called urate rather than by calcium crystals.

Acute CPP crystal arthritis affects men and women in equal numbers, but it's rare for it to affect people under the age of 60. The knee is the most commonly affected joint, although it can affect other joints too.

Many people with osteoarthritis, particularly of the knee, have these calcium crystals in their joint cartilage. This is called osteoarthritis with calcium pyrophosphate crystal deposition (osteoarthritis with CPPD for short) and the symptons tend to be worse than osteoarthritis without crystals.

Symptoms of acute CPP crystal arthritis include:

• severe pain and stiffness in a joint, which comes on quickly and reaches its worst in just 12–24 hours
• swelling and tenderness of the joint
• redness of the skin over the joint
• occasionally fever, a high temperature, causing sweating and a general feeling of being unwell.

The knee is the joint most commonly affected by this condition, but people can also get acute CPP crystal arthritis in the wrist, shoulder, ankle and occasionally other joints. Usually just one joint is affected at a time.

These symptoms tend to last from several days to two weeks. Your joints may be very painful for the first few days. You may notice the swelling going down within a week, though it may take 2–3 weeks for affected joints to get back to normal.

There are several factors that increase your risk of developing crystals. These include:

Age

As we get older, chemical changes happen in the body, which can make it more likely that calcium crystals will form.

Other health conditions

There are several conditions that can lead to calcium crystals forming in your joints and surrounding tissues, and these can sometimes affect younger people. For example:

• If your parathyroid glands, located at the front of the neck, are overactive (this is called hyperparathyroidism) this can result in calcium crystals.
• A condition where there is too much iron in the body (called haemochromatosis) can also lead to acute CPP crystal arthritis.
• More rarely, a lack of the mineral magnesium (called hypomagnesaemia) can also cause acute CPP crystal arthritis.
• If you have osteoarthritis, the concentration of calcium pyrophosphate is increased, making it more likely that crystals will form.

Genes

Research suggests that rarely people may inherit a faulty gene that sometimes leads to calcium crystal diseases.

What triggers an attack of acute CPP crystal arthritis?

The pain and swelling of acute CPP crystal arthritis happens when the crystals shed from the cartilage into the joint cavity.

Often, it’s not clear why the crystals have shed. Sometimes though it will be obvious what has caused the crystals to shake loose. For example, an injury to your knee may shake the crystals loose, causing pain and swelling a day or two afterwards.

Another possible trigger of crystal shedding is an illness that causes a fever, such as having the flu or a chest infection, or a major stress to the body, such as having an operation or a heart attack.

It can be difficult to diagnose acute CPP crystal arthritis as the crystals may be small and difficult to find. And the symptoms may be very similar to other conditions, such as gout, or a joint infection. 

You should see your doctor when you first have symptoms of pain, swelling and redness over a joint. They will examine your joints and ask about your symptoms, and carry out tests to help with the diagnosis and to rule out other conditions or infection.

What tests are there?

There are several tests that can help make a diagnosis of acute CPP crystal arthritis, including:

• testing your joint fluid for crystals or signs of infection
• x-rays and ultrasound scans to show if there are any calcium crystals in the cartilage, excess fluid in the joint, or joint damage
• blood tests to check for:
• inflammation
• too much or too little of the minerals you need to stay healthy – for example, calcium, magnesium or iron
• an infection
• possible problems with your kidneys.

Symptoms of acute CPP crystal arthritis usually settle on their own after a time. But because it can be very painful, you can get treatment to help ease the pain and reduce the inflammation.

Joint aspiration

Your doctor may use a needle and syringe to take extra fluid out of the joint to reduce the swelling and ease pressure in the joint that can cause pain.

This procedure is fairly simple and quick, and it usually brings fast relief. Your doctor will numb the area first so it isn’t too painful.

The excess fluid that's been removed can be examined under a microscope to check for calcium crystals.

Once the excess fluid has been drawn out, your doctor will usually inject a small amount of a steroid into the joint through the same needle. This helps to reduce inflammation in the lining of your joint and prevent the build-up of more fluid.

Applying ice

Applying an ice pack to the painful area can help soothe pain and reduce swelling.

You can buy ice packs, or you could use a pack of frozen peas or ice cubes, wrapped in a damp towel to protect your skin. You can apply ice for about 15–20 minutes at a time.

Non-steroidal anti-inflammatory drugs (NSAIDs)

Non-steroidal anti-inflammatory drugs (NSAIDs) can be used to ease pain and reduce the inflammation caused by the calcium crystals.

NSAIDs include drugs such as aspirin or ibuprofen. Some NSAIDs can be bought from supermarkets or chemists, but others are only available on prescription. They're available as tablets, creams and gels, injections or patches.

NSAIDs aren't suitable for everyone so check with your doctor or a pharmacist if you're not sure.

Colchicine

Colchicine can be used to treat acute CPP crystal arthritis, although it isn't suitable for everyone. It works by reducing the effect the calcium crystals have on your immune system.

Colchicine works best if it's started within 24 hours of the start of the attack.

Steroids

Steroids help to ease symptoms such as swelling, pain and stiffness. They are usually given if you're unable to take NSAIDs or colchicine. The steroids given are corticosteroids, which are different to the anabolic steroids sometimes used by bodybuilders and athletes,

Steroids can be taken as:

• a tablet
• an injection directly into a painful joint
• an injection into a muscle.

As well as the treatments available for acute CPP crystal arthritis, there are ways to manage your symptoms yourself. These include:

Keeping active

Once a flare-up is under control, try to include a bit of exercise in your daily routine. Keeping active can strengthen your muscles, and improve symptoms such as pain or fatigue, as well as being good for your mental health.

If you're new to exercise or haven't exercised in a while, start small and remember that any exercise is better than nothing. You don't need any special gear to get started, and a lot of physical activity can be done at home.

Diet and healthy eating

Calcium crystal diseases aren’t caused by eating too much calcium. In fact, it's important that you have enough calcium in your diet to avoid developing osteoporosis, a condition where your bones can break more easily than usual. You can get calcium from foods such as cheese and yogurt.

For your general health and wellbeing, you should eat a well-balanced diet, that will give you all the nutrients you need such as calcium, vitamin D and iron.

Find out more about eating well with arthritis and related conditions.