MRI scan of the shoulder: why it is done, what to expect and how results work

MRI stands for magnetic resonance imaging. The scanner is a large machine with a short tunnel through it and a flat bed that moves through the scanner. It uses a magnetic field and radio waves rather than X-rays, and the NHS describes it as a scan that takes detailed pictures of the inside of your body. For the shoulder, the scanner is set up to focus on the joint, the surrounding bones and the soft tissues that hold it together and move it.

The shoulder is a complicated area. It is a ball-and-socket joint surrounded by tendons, ligaments and bursae, and shoulder pain can come from any of these. An MRI scan is one of the ways a specialist can look at those structures in more detail than a plain X-ray allows.

The NHS says MRI scans can be used to find out what is causing symptoms you have been having, to check your bones and organs and to see how well a treatment is working. In the shoulder this usually happens after an initial assessment, because most shoulder pain can be managed without a scan.

The NHS advises that shoulder pain can usually be eased yourself, that it can take 6 months or longer to recover, and that you should see a GP if it is getting worse or does not improve after 2 weeks, or if it is very difficult to move your arm or shoulder. The causes it lists include frozen shoulder, arthritis, tendonitis, bursitis, impingement, shoulder instability and a dislocated or broken bone, or a torn or ruptured tendon.

A scan may therefore be requested when the cause is not clear after examination and an X-ray, when treatment such as physiotherapy has not helped, or when a specialist is considering injections or an operation and wants to see the soft tissues first. Your referring clinician will explain which question the scan is meant to answer.

A scan is not the right route for everything. The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you have sudden or very bad shoulder pain, cannot move your arm, your arm or shoulder has changed shape or is badly swollen, you have pins and needles that do not go away, there is no feeling in your arm or shoulder, your arm or shoulder is hot or cold to touch, the pain started after an injury such as a fall, you develop severe pain in both shoulders or you feel feverish or unwell.

It says these can be signs of something serious, like a broken or dislocated bone or a torn ligament or tendon. These situations are assessed face to face first, and any imaging is chosen by the clinician who examines you.

The hospital will tell you if there is anything you need to do. The NHS says you may be asked not to wear anything with metal in it, such as jewellery, a bra, hair clips or hearing aids, to remove coins or keys from your pockets, to change into a hospital gown if your clothes have metal parts such as zips, and not to wear make-up.

You will be asked to complete a form. The NHS says it asks whether you are pregnant or may be pregnant, are breastfeeding, have had surgery before, have any kidney problems, have any metal parts in your body such as surgical clips, a pacemaker, dental fillings or bridges, or have any allergies, including to the dye called contrast medium that is used in some scans. Be thorough with this form: it is a safety check, and previous shoulder surgery with metal implants is exactly the kind of thing the team needs to know.

If you are anxious about the scan or afraid of small spaces (claustrophobia), the NHS advises talking to a healthcare professional at the hospital before your appointment. You may be able to have a medicine to help you relax, and you can ask whether you can bring someone to support you.

An MRI scan is done in hospital by a healthcare professional called a radiographer. You will be asked to lie flat on the bed. You are given ear plugs or headphones because MRI scanners make loud bangs and clicks as they take pictures. The radiographer controls the scanner from another room, and they can hear and speak to you during the scan.

You need to lie still so that the scanner can take clear images, and you may be asked to hold your breath during parts of the scan. For a shoulder scan, the arm on the side being examined is positioned carefully by the radiographer, and a comfortable, supported position makes it easier to stay still. If you were given an injection of contrast medium (dye), it helps show more detail in the pictures.

Afterwards the radiographer comes back into the room to lower the bed so you can get up. If you were given contrast medium you may be asked to wait in hospital for up to 30 minutes to make sure you do not have a reaction. If you had a medicine to relax you, you may be able to go home within a few hours, but someone needs to collect you and you should not drive for 24 hours. Otherwise you can eat and drink as normal.

The NHS says an MRI scan is a common procedure and that serious complications are rare. If you had contrast medium you may get a small bruise where the injection went in, and it can cause side effects that are usually mild, such as feeling or being sick, a skin rash, a headache, a metallic taste in your mouth or feeling dizzy. Allergic reactions are rare, but tell the radiographer if you start to feel unwell during or after the scan.

The images need to be looked at by a specialist called a radiologist, who writes to the doctor who referred you. The NHS says this usually takes between 1 and 2 weeks, that you may need a follow-up appointment to talk about the results, and that if you have not heard anything after a few weeks you should contact the doctor who referred you.

The report will describe what the scan shows in the shoulder, but it needs to be read alongside your symptoms and examination. Scan findings are sometimes present in people with no symptoms at all, so the decision about treatment is made by your clinician rather than by the report wording alone.