Leg MRI

Your healthcare practitioner may not recommend this test in the following conditions:

• During pregnancy: MRI scans are not usually recommended during pregnancy.
• Metallic objects in the body: If you have metal implants, it is important to tell the medical staff about them. They will decide if further measures are needed to ensure your safety during the test.
• Tattoos: Most tattoos are MRI-safe but some tattoo ink may contain traces of metal, which could result in some side effects.

Your healthcare practitioner may order this test in the following conditions:

• Abnormal findings on an X-ray or bone scan
• A mass felt in your leg on physical examination
• Bone pain and fever
• Decreased movement of ankle joint
• Redness/swelling of the ankle joint
• Pain, redness or swelling in leg
• Birth defects of the ankle, foot or leg
• Broken bone
• Leg pain and a history of cancer
• Instability of ankle and foot
• Leg, ankle or foot pain that does not get better after treatment

Normally a contrast dye is not needed, though it does help provide better pictures of some conditions. A contrast MRI of the leg is also done to look for malignancies and tumours.

You may be instructed not to eat/drink for up to six hours before the test. Please inform your healthcare practitioner and the radiologist if you have any of the following:

• Metal fragments (like bullets or shrapnel) inside your body
• Electronic/implanted devices or stimulators
• Implanted drug pumps
• Heart pacemaker/defibrillator
• Stents (not in the heart)
• Filters, such as blood clot filters
• Programmable shunts
• Aneurysm clips and coils
• Ear implants
• Inability to lie on the stomach for 60 minutes
• Pregnancy

If you have a fear of closed spaces, your healthcare practitioner may give you a mild sedative that will make you sleepy and less anxious.

Leave all jewellery and valuables (like keys, watches, etc.) at home, as they cannot be taken inside an MRI room.

An MRI scan usually involves the following steps:

• A radiographer will instruct you to remove all metal objects, including dentures, piercings and hearing aids, before entering the scan room. Even wigs need to be removed, as some wigs contain traces of metal. You may have to wear a hospital gown.
• Your doctor or a radiographer will ask you to lie on the MRI bed, which will slide into the scanner.
• The procedure may require an injection of a dye (contrast), which may be administered through a vein in your arm. The contrast helps to view certain areas more clearly.
• Try to lie very still during the procedure since movements can distort or blur the pictures.
• The test usually lasts about 60 minutes but can take longer.

The bed of the MRI machine may feel hard or cold. You can ask for a blanket or pillow if needed.

An MRI machine makes loud humming or thumping noises during the test, but the radiology staff will provide you with earplugs to block out the noise.

Some people feel a slightly cold sensation as the contrast dye is injected.

A normal result would indicate that there is no problem with your leg. 

An abnormal result may be seen in the following conditions:

• An abscess (collection of pus within a body tissue)
• Degenerative changes due to age
• Arthritis (inflammation of a joint)
• Achilles tendonitis (inflammation of the Achilles tendon which attaches the calf muscle to the heel bone)
• Infection of the bone (Osteomyelitis)
• Broken bone
• Muscle damage
• Injury to tissues like ligament, tendon or cartilage
• Osteonecrosis (a bone disease caused by loss of blood supply to the bone)
• Dysfunction of the posterior tibial tendon which attaches the calf muscle to the bones in the foot
• Rupture of the plantar fascia (thick tissue on the bottom of the foot)
• Tear/rupture of the Achilles tendon
• Tumour or cancer in the muscle, bone or soft tissue

The following risks are associated with this test:

• The strong magnetic field created by the MRI machine may disrupt the normal functioning of pacemakers and other metal implants. It may also move the implants within the body.
• Contrast dye may cause temporary headaches, dizziness and nausea for some.
• The contrast used can be harmful to people with kidney diseases that require dialysis.
• Rarely, an allergic reaction to the contrast can occur.

The benefits of this test include:

• It does not use radiation.
• The test is generally painless.
• It gives a detailed diagnostic picture.

You can continue with your daily activities soon after the test. However, if a sedative was given, follow the precautions mentioned below:

• You must have someone with you for 24 hours after the test.
• You must not drive a vehicle or use public transport till the effects of the sedative wear off.
• On the day the test is performed, avoid operating heavy machinery.

A non-contrast MRI is mostly used to detect conditions of the legs; however, contrast MRI of the leg is done in some cases to get more distinct images of tissues and to detect and differentiate benign and malignant lesions of the leg. Some of the lesions are as follow:

• Benign lesions:
  • Plantar fibromatosis
  • Deep fibromatosis
  • Haemangioma
  • Angiomyoma
  • Synovial osteochondromatosis
• Malignant lesions:
  • Synovial sarcoma
  • Rhabdomyosarcoma
  • Lymphoma
  • Melanoma

Contrast MRI is also used to detect Morton’s neuroma in the leg.

The dye temporarily binds to certain tissues and then is gradually eliminated through urine. Most healthcare practitioners use gadolinium as the contrast dye for MRI. The dye is considered to be safe but may be harmful to those undergoing dialysis. Also, some people get a headache with dizziness and vomiting after the dye is injected.

Your healthcare practitioner may order other tests along with a leg MRI depending on the condition under investigation. For example:

• Biopsy (for bone tumours/inflammation)
• Bone scans (for inflammation in the bone)

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.