MRI Knee – detailed imaging for knee pain and suspected injury

An MRI of the knee provides detailed images of the knee joint and surrounding soft tissues. The examination can assess the menisci, cruciate ligaments, collateral ligaments, cartilage, tendons, bone marrow, and other structures that may be difficult to evaluate with standard X-rays.

Knee MRI may be appropriate for persistent or recurring knee pain, swelling, instability, or after a twisting injury or sports-related trauma where an internal knee injury is suspected. MRI does not use ionising radiation.

The most appropriate imaging method depends on your symptoms and how the problem started. A medical assessment is therefore included to help determine whether a knee MRI is the right examination for your specific symptoms and clinical question.

Knee pain – when can an MRI be helpful?

Knee pain is common and can have many different causes. Symptoms may arise from the menisci, ligaments, cartilage, tendons, bone, or other structures in and around the knee joint.

An MRI is not necessary for every type of knee pain. Short-term symptoms may be better assessed initially with a clinical examination, rehabilitation, or another imaging method. MRI can be particularly useful when symptoms persist or when there is suspicion of an internal knee injury that cannot be fully evaluated through clinical examination or plain X-ray.

An MRI of the knee may be appropriate for:

• Persistent or recurring knee pain.
• Pain after a twisting injury, fall, or sports injury.
• Swelling or recurrent fluid accumulation in the knee.
• Instability or a feeling that the knee gives way.
• Locking or significant mechanical symptoms.
• Suspected meniscal injury.
• Suspected ACL, PCL, or other ligament injury.
• Suspected cartilage or osteochondral injury.
• Unexplained symptoms where previous examinations have not provided enough information.
• Follow-up of certain previously diagnosed knee injuries or abnormalities.

What can an MRI of the knee show?

MRI provides detailed images of both soft tissues and the internal structure of bone. This makes it useful for assessing several important parts of the knee joint.

• The medial and lateral meniscus.
• The anterior and posterior cruciate ligaments, ACL and PCL.
• The medial and lateral collateral ligaments, MCL and LCL.
• Articular cartilage and joint surfaces.
• The kneecap and structures around the patellofemoral joint.
• Tendons and other soft tissues around the knee.
• Bone marrow changes, including bone marrow oedema and stress reactions.
• Joint fluid, synovitis, and certain inflammatory changes.

MRI findings should always be interpreted together with your symptoms and clinical assessment. Changes can sometimes be seen on MRI even in people who do not have any knee symptoms.

Common reasons for a knee MRI

MRI knee for suspected meniscus tear

The menisci act as shock absorbers and contribute to stability within the knee joint. A meniscal tear can occur after a twisting injury, but degenerative meniscal changes can also develop gradually with age and may occur together with osteoarthritis.

Possible symptoms include pain along the joint line, swelling, clicking, or a feeling that the knee catches during movement.

MRI can provide detailed images of the menisci and help assess whether a tear or other structural change is present. It can also show whether other structures in the knee have been injured at the same time.

It is important to distinguish between an acute traumatic meniscal injury and age-related degenerative meniscal changes. MRI findings alone do not determine whether surgery is needed, and many meniscal problems are managed without an operation.

MRI knee for ACL and cruciate ligament injuries

The cruciate ligaments help stabilise the knee. An anterior cruciate ligament injury, or ACL injury, is particularly common in sports and can occur during sudden twisting, pivoting, or changes in direction.

Symptoms may include sudden pain, rapid swelling, and later a feeling that the knee is unstable or gives way. ACL injuries can also occur together with meniscal tears, cartilage injuries, or other ligament damage.

MRI can assess both the ACL and PCL and help determine whether a cruciate ligament has been injured, as well as whether other structures in the knee are affected.

MRI for collateral ligament injuries

The medial and lateral collateral ligaments, MCL and LCL, contribute to side-to-side stability of the knee. These ligaments can be injured when the knee is exposed to force from the side or during more complex twisting injuries.

MRI can assess changes in these ligaments and can also identify associated injuries within the knee joint.

MRI for cartilage damage and osteoarthritis

MRI can provide detailed images of the articular cartilage and can show changes in cartilage, bone marrow, and other structures within the joint.

This does not mean that MRI is routinely required for suspected knee osteoarthritis. Osteoarthritis is usually assessed primarily through symptoms and clinical examination and may sometimes be supplemented with standard X-rays.

MRI may be useful for more specific questions, for example when symptoms are not fully explained by the clinical findings or when another internal knee injury is suspected.

Symptoms that may lead to a knee MRI

Swollen knee – can MRI identify the cause?

A swollen knee can have several causes, including an internal joint injury, irritation of the joint lining, bleeding following trauma, or inflammation.

MRI can demonstrate joint fluid while also assessing the menisci, ligaments, cartilage, and bone marrow. However, sudden or severe swelling after an injury may require prompt medical assessment before a planned MRI examination.

Knee locking, clicking, or giving way

Mechanical symptoms in the knee can be described in different ways. Some people experience clicking or catching, while others feel that the knee suddenly gives way.

These symptoms can occur with meniscal tears, ligament injuries, or other structural problems, but they need to be interpreted together with the rest of the clinical picture.

If the knee becomes genuinely locked and cannot be moved normally, a prompt medical assessment is recommended rather than waiting only for a planned MRI.

Pain on the inside or outside of the knee

The location of knee pain can provide some clues about which structures may be involved, but the cause cannot be determined from pain location alone.

Pain on the inside of the knee may be associated with the medial meniscus, medial collateral ligament, or other nearby structures. Pain on the outside of the knee can have different causes.

MRI may be appropriate when symptoms persist and there is suspicion of a structural problem within the knee joint.

Knee pain after running or exercise

Knee pain after running or exercise is common and does not necessarily mean that an MRI is needed. Many overuse-related problems are best assessed clinically and initially managed with activity modification and rehabilitation.

If pain persists, keeps returning despite treatment, or is accompanied by swelling, locking, instability, or other signs of internal injury, a medical assessment can help determine whether MRI is appropriate.

MRI knee after a sports injury or twisting injury

Sports-related knee injuries often occur during sudden changes in direction, rotation, impact, or awkward landings. Common internal knee injuries include meniscal tears, ACL injuries, collateral ligament injuries, cartilage damage, and kneecap dislocation.

MRI can be valuable when a medical assessment suggests an internal soft tissue injury or when several structures may have been damaged at the same time.

Following acute trauma, MRI is not always the first examination. Depending on the circumstances, a clinical assessment and plain X-ray may be needed first to rule out fractures or other urgent injuries.

MRI knee or X-ray – what is the difference?

MRI and standard X-ray show different structures and are therefore useful for different clinical questions.

X-rays primarily show bone and may be important when a fracture is suspected or when assessing certain degenerative changes.

MRI provides much more detailed information about the menisci, cruciate ligaments, other ligaments, cartilage, bone marrow, and many other soft tissues within the knee joint.

Following acute knee trauma, an X-ray may therefore be required first, while MRI can be used later if a soft tissue injury needs more detailed assessment.

Is contrast needed for a knee MRI?

For common questions such as meniscal tears, cruciate ligament injuries, collateral ligament injuries, or cartilage damage, a knee MRI is usually performed without intravenous contrast.

Contrast may be required for certain more specific clinical questions. This is determined according to the reason for the examination and the MRI protocol being used.

What happens during an MRI of the knee?

During the examination, you lie on your back with the knee positioned in a dedicated MRI coil that helps produce detailed images of the joint.

It is important to remain as still as possible while the images are being taken. The examination itself is painless, although the MRI scanner produces loud knocking and tapping sounds during parts of the scan. MRI does not use ionising radiation.

The total examination time depends on the MRI protocol being used. You will receive information about the examination and any necessary preparations beforehand.

When is a knee MRI not the best first examination?

MRI is not required for every type of knee pain. Short-term overuse symptoms, uncomplicated osteoarthritis, or certain acute injuries may need to be assessed in other ways first.

For suspected osteoarthritis, diagnosis is usually based mainly on symptoms and clinical examination, with standard X-rays used when appropriate. MRI is not routinely needed in uncomplicated cases.

Following a significant recent injury, an X-ray or urgent orthopaedic assessment may be more important than a planned MRI.

It is also important to remember that an MRI finding does not automatically mean that the abnormality is causing your symptoms or that surgery is necessary.

When should knee symptoms be assessed urgently?

Certain knee problems should be assessed promptly rather than through a routine planned MRI appointment.

This may apply if:

• The knee is locked in one position and cannot be moved normally.
• There is an obvious deformity after an injury.
• The knee is severely unstable following trauma.
• There is very marked swelling or suspected bleeding into the joint after injury.
• There is concern about a fracture following significant trauma.

These situations may require prompt clinical assessment and, in some cases, different imaging or orthopaedic treatment.

Book an MRI of the knee

An MRI of the knee can provide detailed information about the menisci, cruciate ligaments, other ligaments, cartilage, bone marrow, and surrounding soft tissues. It can be particularly useful for persistent knee pain or when symptoms suggest an internal knee injury.

You do not need to decide on your own whether MRI is the most appropriate examination. A medical assessment is included as part of the booking process to review your symptoms and clinical question. If an X-ray, physiotherapy assessment, or another type of investigation is considered more appropriate, this can be recommended instead.

The MRI images are reviewed by a specialist radiologist, and the findings are summarised in a medical report.