Knee Pain: When Do You Need an MRI?
One of the most common questions I am asked by people with persistent knee symptoms is whether they need an MRI for knee pain.
Sometimes the answer is yes.
An MRI can provide extremely useful information about structures within the knee and, in the right circumstances, can help guide decisions about treatment or surgery.
But not every painful knee needs an MRI.
In fact, one of the challenges with knee imaging is that MRI scans frequently identify abnormalities that may not actually be responsible for somebody's symptoms. Meniscal tears are a particularly good example.
The important question is therefore not simply whether an MRI might find something.
It is whether the scan is likely to provide information that changes what we do next.
Table of Contents
Can knee pain be diagnosed without an MRI?
Very often, yes.
A detailed history and clinical examination can provide a considerable amount of information about what is likely to be causing knee pain.
The assessment might consider:
Where the pain is located
How and when it started
Whether there was an injury
Swelling
Movement
Strength
Stability
What activities provoke the symptoms
Whether there is clicking, catching or locking
How the symptoms have changed over time
Age and activity are also important.
A 22 year old footballer whose knee twisted and rapidly swelled during a tackle presents a very different clinical question from a 58 year old whose knee has gradually become painful when walking and using stairs.
Neither presentation should simply be reduced to:
“Let's get an MRI and see what's there.”
The clinical assessment should establish a working diagnosis first and determine whether imaging is actually required.
What does a knee MRI show?
MRI provides detailed images of many of the structures within the knee, including:
Menisci
Anterior and posterior cruciate ligaments
Articular cartilage
Bone
Tendons
Muscles
Other soft tissues
That makes MRI extremely useful when we need detailed structural information.
But its sensitivity is also part of the problem.
If we scan enough knees, particularly as people get older, we frequently find structural abnormalities.
Finding an abnormality and establishing the cause of somebody's pain are not necessarily the same thing.
Does a meniscus tear on MRI mean it is causing your pain?
No.
This is one of the most important things to understand about knee MRI.
A landmark study published in the New England Journal of Medicine investigated meniscal findings in middle aged and older adults from the general population.
Meniscal damage was common and increased substantially with age, ranging from around 19% in women aged 50 to 59 to 56% in men aged 70 to 90.
Perhaps more importantly, the majority of meniscal tears were found in people who did not have knee pain, aching or stiffness.
That does not mean meniscal tears never cause symptoms.
They absolutely can.
It means that seeing the words “meniscal tear” on an MRI report does not automatically establish the diagnosis.
The finding needs to be interpreted alongside the history and clinical examination.
This is particularly important with degenerative meniscal changes in middle aged and older adults.
Without that context, somebody can understandably conclude that something inside their knee is torn and needs to be repaired or removed when the situation may be considerably more nuanced.
Does a meniscus tear need surgery?
Not necessarily.
There is an important distinction between different types of meniscal problems.
A significant acute traumatic injury in a younger person is different from a degenerative meniscal tear identified on an MRI in somebody in their fifties or sixties.
For degenerative meniscal tears, there is now strong evidence supporting exercise based treatment.
The ESCAPE randomised clinical trial compared exercise based physiotherapy with arthroscopic partial meniscectomy in 321 people aged 45 to 70 with degenerative meniscal tears.
At five years, exercise based physiotherapy remained noninferior to arthroscopic surgery for knee function. The researchers concluded that physiotherapy should be the preferred treatment for degenerative meniscal tears.
Again, this does not mean that meniscal surgery is never appropriate.
It means that the presence of a tear on an MRI is not, by itself, an indication for an operation.
The type of tear, mechanism, symptoms, function, clinical findings and response to appropriate conservative management all matter.
When is an MRI useful for knee pain?
There are several situations where an MRI for knee pain can be extremely useful.
Significant acute knee injuries
Following a substantial twisting or sporting injury, there may be concern about damage to structures such as the ACL, other ligaments or meniscus.
The history and examination may already create strong suspicion of a particular injury.
MRI can then help confirm the structural damage and assist with decisions about rehabilitation or surgical management.
An uncertain diagnosis
Sometimes the clinical assessment does not provide enough certainty.
If several diagnoses remain plausible and the result would change management, imaging can provide useful additional information.
Persistent symptoms that are not behaving as expected
If somebody has completed appropriately structured rehabilitation but symptoms are not progressing as anticipated, reassessment is important.
MRI may then become useful.
That does not mean everybody whose knee still hurts after six weeks needs a scan.
The question is whether the clinical situation has reached a point where additional structural information would meaningfully influence what happens next.
When surgery is genuinely being considered
If the clinical picture suggests that an orthopaedic intervention may be appropriate, MRI can provide important information for surgical decision making.
In each of these situations, there is a reason for obtaining the scan.
We are trying to answer a particular clinical question rather than simply looking for abnormalities.
When might an X ray be more useful than an MRI?
MRI is more detailed, but more detailed does not automatically mean more appropriate.
If the main clinical question is whether somebody has significant knee osteoarthritis, a weight bearing X ray may provide the information required.
X rays are particularly useful for assessing joint space and other structural changes associated with osteoarthritis.
An MRI may subsequently identify meniscal damage, cartilage abnormalities and numerous other changes, but these may add very little if the clinical picture and X ray already provide the information needed to guide management.
The appropriate investigation therefore depends on the question being asked.
Sometimes that is an MRI.
Sometimes it is an X ray.
And sometimes no imaging is required at all.
Does clicking or catching mean you need an MRI?
Not automatically.
Knees make noises.
Clicking, cracking and other sensations are extremely common and are not necessarily evidence of significant structural damage.
Even intermittent catching does not automatically mean that a piece of meniscus is physically getting stuck inside the joint.
The details matter.
Is it painful?
Is there swelling?
Did it begin following an injury?
Can the knee fully straighten?
Does the knee actually become mechanically stuck?
Are the symptoms becoming more frequent?
Those questions are considerably more useful than the presence of clicking alone.
What is a genuinely locked knee?
The term “locking” is used quite loosely.
People sometimes describe a knee as locking when it feels stiff, painful or temporarily difficult to move.
A genuinely locked knee is different.
The knee becomes mechanically unable to fully straighten, potentially because something within the joint is physically blocking movement.
A displaced meniscal tear is one possible cause.
That presentation deserves timely assessment because it may change the urgency of imaging and orthopaedic management.
This is very different from occasional clicking or a brief catching sensation in an otherwise freely moving knee.
Understanding exactly what somebody means when they say their knee is “locking” is therefore important.
What if your knee pain is not improving with physiotherapy?
Persistent knee pain does not automatically mean that you need an MRI.
But it should prompt reassessment.
The first question is whether the diagnosis still makes sense.
The second is whether conservative management has genuinely been optimised.
Being given several exercises and s
till having pain does not necessarily demonstrate that physiotherapy has failed.
Rehabilitation needs to consider the individual's strength, capacity, symptoms and goals.
The appropriate exercise needs to be selected.
The load and dosage need to be sufficient.
The programme needs to progress.
And ultimately, rehabilitation needs to prepare the knee for whatever the individual actually wants to return to.
For one person that might be walking comfortably around the golf course.
For another it might be running, skiing or playing competitive sport.
If the diagnosis remains uncertain, progress has plateaued despite appropriately progressed rehabilitation, or the result of imaging would influence treatment, an MRI may then be entirely appropriate.
The answer is not to avoid imaging.
It is to use imaging when it adds something useful.
When should you get an orthopaedic opinion?
An orthopaedic opinion may be appropriate when there is a genuine surgical question.
That could follow a significant traumatic injury, a mechanically locked knee or persistent symptoms where appropriate conservative management has not produced an acceptable outcome and the clinical findings suggest surgery may reasonably be considered.
An MRI will often form part of that process.
But neither an MRI abnormality nor persistent pain automatically means that a surgeon is the next step.
Sometimes the more useful question is whether the diagnosis is correct and rehabilitation has genuinely been optimised.
This is where an Advanced Physiotherapy assessment can be particularly useful.
The role is not to be anti scan or anti surgery.
It is to understand the clinical presentation first.
Does this look like osteoarthritis?
Is the meniscal finding actually likely to be clinically relevant?
Could the symptoms be coming from the patellofemoral joint?
Has there been a significant ligament injury?
Is imaging likely to change management?
Has conservative treatment genuinely been optimised?
Is there now a clear reason for an orthopaedic opinion?
Those are clinical reasoning questions.
At Genuine Physio in Tadworth, near Kingswood, my role as an Advanced Physiotherapist is to assess the whole clinical picture and help determine the most appropriate next step.
Sometimes that is rehabilitation.
Sometimes an X ray is enough.
Sometimes an MRI is exactly what is needed.
And sometimes an orthopaedic opinion is appropriate.
The value is knowing the difference.
Frequently Asked Questions
Do I need an MRI for knee pain?
Not necessarily. Many causes of knee pain can initially be assessed through the history and clinical examination. MRI becomes more useful when the diagnosis is uncertain, there has been a significant injury, symptoms are not progressing as expected or the result is likely to change management.
Can a knee MRI show the cause of my pain?
It can identify structural abnormalities, but an abnormality does not automatically identify the cause of pain. MRI findings need to be interpreted alongside your symptoms and clinical examination.
Does a meniscus tear on MRI mean I need surgery?
No. Meniscal tears are common, particularly as people get older, and many exist without symptoms. High quality research also shows that exercise based physiotherapy can produce outcomes comparable with arthroscopic partial meniscectomy for degenerative meniscal tears.
Is an MRI or X ray better for knee pain?
It depends on the clinical question. An X ray may be more appropriate when assessing suspected osteoarthritis, while MRI provides more detailed information about structures such as the menisci and ligaments. Neither is automatically the correct investigation for every painful knee.
Do I need an MRI if my knee clicks?
Usually not simply because it clicks. Clicking is extremely common. Pain, swelling, injury history, loss of movement and genuine mechanical locking provide much more useful information.
What does it mean if my knee is locked?
A genuinely locked knee cannot fully straighten because movement is mechanically blocked. This is different from a knee that feels stiff or occasionally catches and should be assessed promptly.
Should I get an MRI if physiotherapy has not worked?
Possibly, but persistent symptoms should first prompt reassessment. The diagnosis, rehabilitation programme and progress should be reviewed. If imaging would then provide information that changes management, an MRI may be appropriate.
Unsure whether you need an MRI for knee pain?
If your knee pain is persisting and you are unsure whether you need an MRI, further rehabilitation or an orthopaedic opinion, get in touch with Genuine Physio.
A detailed assessment can help establish the likely diagnosis, determine whether conservative management has genuinely been optimised and decide whether imaging would provide useful additional information.
The aim is not to avoid an MRI.
Nor is it to scan every painful knee.
It is to use the right investigation, for the right person, at the right time.
Comments