An ACL injury is a tear or sprain of the anterior cruciate ligament (ACL), which is one of the strong bands of tissue that help connect the thigh bone to the shinbone.
This type of injury is most common in athletes and sporting professionals who make a lot of sudden stops or changes in motion. It is most commonly seen in football, basketball, rugby, wrestling, and skiing.
Depending on your symptoms, your doctor might refer you to get an MRI scan which can help confirm the severity of your tear, identify any other surrounding injuries, and determine if surgery is needed.
How Do ACL Rupture MRI Scans Work?
An MRI uses radio waves and a strong magnetic field to take images of the hard and soft tissues within your body, which in this case would be your knee. It’s a non-invasive medical imaging procedure that can help doctors take stock of the extent of your injury without more invasive procedures, such as surgery.
Many doctors prefer using MRIs because they can show the extent of your injury as well as other injuries on the surrounding tendons, ligaments, and muscles. The results of your MRI will help your doctor come up with a treatment plan, which may include surgery.
Why Might You Need an ACL Rupture MRI?
Other ways to diagnose an ACL tear include an X-ray, which can help rule out a bone fracture, and an ultrasound, which uses sound waves to visualise the internal structures of the muscles, ligaments, and tendons of the knee. However, X-rays can’t show soft tissues like ligaments and tendons, and ultrasounds often result in less clear images, so many doctors are now turning to MRI machines to identify more information about your injury to improve your treatment plan.
An MRI scan can streamline treatments to make sure you’re getting the best, including helping plan surgery to keep it short instead of the doctors finding extra injuries to fix while you’re on the operating table.
How To Prepare for Your ACL Rupture MRI?
There isn’t much preparation you need to do before your MRI scan for an ACL rupture, as most MRIs are performed quite quickly after the injury has been sustained. However, if your scan is planned and you’re preparing before the day, there are a few things you can do.
First of all, the MRI scanner features a massive magnet, so nothing metal can be worn into the room. This includes jewellery, keys, watches, cards, and electronics, so make sure you remove as much of this as possible before going into the hospital. Leaving the metal at home will reduce your wait time and get you into the scanner quicker.
It’s also important to tell your doctor if you have any metal medical devices such as pacemakers, plates or pins, and dental retainers, as these can also affect whether you can use the MRI machine.
There shouldn’t be any restrictions on drinking, but some doctors might ask you not to eat for one hour before your appointment. However, your doctor will have more information on how to prepare for your specific MRI, as different trusts have separate rules.
What To Expect From an MRI Scan of Your Leg
During the Scan
Once you’re checked into the hospital for your MRI appointment, the radiology staff will verify your identification and provide you with the clothes you need to change into. This will include a gown, socks, and maybe underwear. Your clothes will be placed in a locker for safe-keeping and you’ll be advised to remove jewellery, keys, and more during this stage. If you wear hearing aids, you’ll also be asked to remove these and leave them in your locker. While it may be frustrating, the MRI scanner can cause damage to the hearing aids.
Some MRI exams will use a contrast agent to help the technologist get a better image of your knee joint. Most orthopaedic scans are done without this, but if your radiologist calls for it, you’ll be set up with an IV catheter to inject the agent later in the scan.
Once you’re ready for the scan, your technologist will position you in the scanner. There are quite a few loud noises while the scanner is on, so you might be given headphones and a choice of music to keep you calm during the 45- to 60-minute scan.
You’ll need to lie completely still during the scan, and your leg may be strapped down to keep it in position. You’ll be able to talk to your radiologist the entire time you’re in the scanner, so feel free to let them know if you have any issues or are feeling uncomfortable.
After the Scan
After your scan is complete, you’ll be taken back to your locker so you can change back into your clothes and retrieve your personal belongings. If you had an IV for the contrast agent, this will be removed before you can go home. Allergic reactions are extremely rare to the contrast agent, but if you notice any symptoms, your doctor might ask you to wait in the hospital for a few hours for monitoring.
Some hospitals might offer sedatives to patients who are nervous about feeling claustrophobic. If you’ve been given a sedative, you’ll either be asked to wait for it to wear off or make sure you have someone else to drive you home.
What Are the Benefits of an MRI Scan of the Leg?
There are several benefits of an ACL rupture MRI, including:
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MRI scans can help determine the severity of your injury: ACL ruptures can affect more than just the ACL, including muscles, tendons, and ligaments, so an MRI can help see more injuries sustained other than the initial tear
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MRIs are non-invasive: Many doctors like MRI scans so much because they’re non-invasive and can easily determine plenty about the injury without surgery
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The images can help plan your surgery: Some ACL tears will need surgery to reconstruct the ligament, which can be time-consuming and tricky, so having a clear image of what’s going on inside your leg can help doctors customise your surgery plan and make it as efficient as possible
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MRIs produce clear images: Other ways to detect an ACL tear include ultrasounds and X-rays, but these don’t produce as clear and detailed images as an MRI machine
What Are the Risks of an MRI Scan of the Leg?
There are very few risks of being given an MRI scan of the leg as the machine can create images without the use of ionising radiation. However, as the machine uses a large magnet, it’s vital that you remember to disclose any medical devices you have to your doctor as these can affect the machine and potentially be dangerous. This is why you need to remove all metal before your appointment and talk with your doctor about past surgeries that may have used metals for treatment.
In rare cases, orthopaedic MRIs will use contrast agents to see the internal structures of the leg easier. Very few people have had an allergic reaction to this, so it’s important to tell your doctor if you have a history of allergic reactions so they can prepare if they want to give you the agent during your scan.
Other Common MRI Scans
As well as orthopaedic MRI scans, several other types of MRI scans are used to assess different parts of the body. These include:
These scans will all use the same method of scanning, but the body part positioned in the middle of the scanner will be different. The same ideas and procedures apply, though, although a contrast agent might be more likely with other MRI scans of the body.
Your doctor will be able to assess and refer you to the correct kind of MRI scan you need.
FAQs
Why Would a Doctor Order an MRI of Your Leg?
When you believe you’ve sustained an ACL tear, your doctor may use an X-ray or ultrasound doppler to take a look. These might not be able to see the full extent of your injury, so they may then order an MRI to determine the severity of your injury and help tailor your treatment plan to your individual circumstances.
How Long Does an ACL Rupture MRI Take?
Most ACL tear MRI scans take around 45 to 60 minutes, although it will depend on your technician and the preparation work you need before the scan actually begins. You should be able to go home straight away, although you may be asked to wait behind if you are having an allergic reaction, have been given a sedative, or are waiting for someone to drive you home.
Can I drink water before an ACL Rupture MRI?
There should be no restrictions on drinking water before an MRI scan, but we recommend talking to your doctor beforehand to make sure this isn’t something your health board requests. Drinking water before your scan when your health board asks you not to may result in your scan being pushed back to a later date.
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