Joint Injection

Author: A/Prof Howard Galloway*

What is a joint injection?

A common cause of a painful joint is synovitis (inflammation of the lining of the joint). An injection of corticosteroid and/or local anaesthetic medication directly into the joint can sometimes be helpful in reducing the inflammation and providing pain relief. Reduction in pain may make physical therapy more effective.

This procedure is most often used in the shoulder, knee or hip, but may also be helpful in other joints.

To make sure the injection goes into the joint itself where it has a better chance of working, the injection needle is guided by using pictures or images, most often using ultrasound. X-ray or computed tomography (CT) can also be used for guidance.

Sometimes it can be difficult for the referring doctor to know exactly what is causing the joint pain. If the pain is not due mainly to joint inflammation, the injection may not improve the symptoms. Although this might be disappointing for the patient, it can be helpful information for the doctor, as it means that another cause of the joint pain needs to be considered.

A joint injection can also be carried out as part of another more detailed imaging scan of the joint. This is usually either CT or magnetic resonance imaging (MRI) and in these cases dye (contrast medium) is injected into the joint for more detailed images (see InsideRadiology: Arthrogram).

Why would my doctor refer me to have this procedure?

Your doctor may request a joint injection using imaging guidance when:

• there is known inflammation in the joint not improving with other treatments;
• pain is present in the region of a joint and your doctor wants to know if the joint itself is responsible for your symptoms;
• special medications or treatments need to be injected directly into the joint and not in the surrounding soft tissues;
• it forms part of a more detailed scan of your joint (i.e. arthrogram); or
• your doctor has attempted and failed to inject directly into the joint without using imaging guidance (e.g. in the consulting room).

How do I prepare for a joint injection?

Before your appointment day:

• You do not need to do anything special before a joint injection. You may eat and drink as normal.

On the day of your appointment:

• Please take any previous X-rays, ultrasound, CT or MRI scans taken as part of your joint pain history.
• Please tell the radiologist (specialist doctor) if you are allergic to any medications.
• It may be best to wear comfortable clothing with easy access to the joint being injected.

What happens during a joint injection?

The joint injection is most commonly carried out using ultrasound to guide the injection. X-ray or CT can be used depending on the joint to be injected and the method preferred by the radiologist (specialist doctor) who carries out the injection.

Generally a preliminary scan will be done to locate the exact point to be injected, which may be marked on your skin. The skin will then be cleaned with an antiseptic solution to prevent infection.

A needle will be placed into the joint either at the point marked on your skin or using the ultrasound to see the tip of the needle as it moves into the joint. If CT or X-rays are used to guide the needle, then a small amount of contrast medium will be injected into the joint to provide clearer images and ensure the needle tip is correctly positioned.

Sometimes the radiologist may remove some fluid from the joint for analysis before giving the injection. The injection itself is usually a mix of steroid and/or local anaesthetic.

Are there any after effects of a joint injection?

You may experience more soreness in the joint after the injection, but may also feel better initially as a result of the local anaesthetic. The anaesthetic will generally wear off after a few hours and you may have more soreness in the joint than before the injection. This soreness may last for 2–3 days after the injection.

If the steroid part of the injection is going to reduce the pain and inflammation in the joint, this will usually start to occur between 3–5 days after the injection.

If the pain becomes much worse in the days after the injection, this may indicate either an aggravation of the synovitis by the injection or very rarely an infection of the joint. If this occurs, you should contact your referring doctor or the emergency department of a hospital as soon as possible.

How long does a joint injection take?

This can vary, but an ultrasound-guided injection will generally take between 15 and 30 minutes.

What are the risks of a joint injection?

This is a very safe procedure with few risks.

There is a risk of infection, which is very small and probably lies between 1 in 20,000 and 1 in 75,000 injections carried out. The procedure should not be done if there is broken skin or infection overlying the joint, or if the joint may already be infected.

There are possible complications of the steroid injection, which include aggravation of the pain due to irritation of the joint lining by crystals in the steroid solution.

If the steroid is not injected solely into the joint or leaks out of the joint after the injection, there is a risk of minor damage to the soft tissues at the injection site, including atrophy (a weakening) of the skin or subcutaneous fat (found just beneath the skin). Occasionally, a localised area of skin depigmentation can occur at the injection site.

Some patients find that the injection gives them good pain relief for a few months, but then the pain comes back and they wonder about having another injection. Although the exact risk of multiple injections is not known, most doctors would advise against having the injection more than three or four times a year to avoid damage to the joint.

Occasionally, people are allergic to the injected medication (as with any drug). The exact risk of this is not known, but it seems to be very uncommon. You should advise your doctor and the radiologist carrying out the joint injection of any allergies you may have.

What are the benefits of a joint injection?

Joint injections confirm if the injected joint is the site of pain, and reduce the synovial inflammation to reduce the pain and enable you to have physical therapy.

Overall, steroid injections into joints (particularly the shoulder and the knee) appear to provide short- to medium-term pain relief (3 weeks to 3 months), particularly when combined (in the shoulder) with appropriate physical therapy.

They do not provide long-term pain relief and do not alter the course of underlying joint disease (e.g. osteoarthritis).

Who does the joint injection?

The joint injection is carried out by a specialist doctor (radiologist) who uses an ultrasound machine, or less commonly fluoroscopy or a CT scan, to guide the needle into the joint.

The radiologist will provide a written report to your doctor about the procedure.

Where is a joint injection done?

Usually in either a public or private hospital, or a private radiology practice

When can I expect the results of my joint injection?

A report on the joint injection will be sent to your referring doctor. It is important, a week or so after the injection, that you inform your doctor as to whether the injection has had any effect on your pain.

*The author has no conflict of interest with this topic.

Page last modified on 31/8/2018.