Ask Dr. Geier – Is an MRI necessary to diagnose an ACL injury?

Hey everyone! It’s time for another Ask Dr. Geier column. This week I address an interesting question about the true need for MRI studies after particular injuries.

I want to remind you that I answer about four to six readers’ questions on my show each week. So if you have a question, or if you just like hearing me discuss sports injuries, treatments, surgeries, and prevention, please check out The Dr. David Geier Show.

As always, while I appreciate your questions, please remember that I cannot and will not discuss specific medical information by email, online, or on my show. My responses are meant to provide general medical information and education. Please consult your physician or health care provider for your specific medical concerns.


Jesse asks:

Hello doctor, first let me say, I just discovered your site and podcast and will be recommending both to my friends.

I am researching ACL information as my girlfriend injured her knee 18 months ago while playing rugby. After some recovery she found that some instability remained and requested a referral to a sports doc. He reckoned an ACL tear on the strength of some in-clinic load tests and sent her for x-rays and to a surgeon.

She has since moved and gone through the same procedure of load tests and x-rays in her new local.

We live in Canada and while there is socialized medicine, there is a queue for services and it is my guess that that is why no MRI.

My question is: in a perfect world would you send every patient where ligament damage is suspected for an MRI or perhaps a CT scan?

Thank you for your time and the excellent website!


Thank you so much for the feedback on the website. I am really glad it has been helpful to you! I definitely have some thoughts on your question. I don’t really want to address the politics of healthcare in Canada (even though I actually know a fair amount about it with relatives in Canada…). My comments pertain to the use of MRI studies to diagnose ACL tears in general.

Lachman's test
A sports medicine surgeon performs a Lachman’s test to assess integrity of the ACL.
A sports medicine physician can fairly often correctly diagnose an ACL injury on the sidelines after it occurs or in the clinic. When the athlete describes the way the injury occurred, she often gives one of the classic noncontact mechanisms. Typical ACL injury mechanisms include landing from a jump with the knee fully extended or planting the foot to change directions. She might remember feeling or hearing a loud pop and her knee buckling as she fell to the ground. The explanation of the injury often raises a red flag for a sports medicine physician that she has torn her ACL.

Also, physical examination tests can accurately reveal the injury. If a healthcare provider can examine the player before her knee swells and the muscles tighten up, these ACL tests easily demonstrate a lack of stability in the knee. That is one reason I often tell our orthopaedic surgery residents to believe the athletic trainers when they suspect a player has torn her ACL. They examine the knee before swelling and guarding develop, so their exams are frequently accurate.

Once swelling and stiffness of the knee develop, the injured athlete often guards against these tests in the clinic. In this phase (usually between 24 hours and 7 days or so), it can be difficult to get the patient and her lower extremity to relax enough to get clear results with these maneuvers. If the diagnosis is unclear, ordering an MRI might be reasonable.

Meniscal repair
The surgeon can often use sutures or other devices to repair a meniscus tear if one is found during the arthroscopy of the knee.
If the ACL tests clearly suggest an ACL injury, then an MRI isn’t always needed. Obtaining an MRI to look at the other structures in the knee may or may not be necessary. The surgeon does look at the other structures in the knee arthroscopically when performing the ACL reconstruction.

For instance, knowing whether or not there is a coexisting meniscus tear isn’t always required, as the surgeon is prepared to trim or repair the meniscus if a tear is found. On the other hand, if the surgeon suspects multiple ligaments are injured, an MRI might be warranted, as that knowledge would potentially change the surgical plan.

I would point out that ordering an MRI for an acute knee injury is not necessarily wrong. I know I have questioned the routine use of MRI studies for evaluation of knee pain in every single patient previously. If the diagnosis of ACL tear is unclear, if there is concern for a multi-ligament knee injury, or if athletes, parents, or sports teams specifically want one, I think that an MRI can be useful.

13 Responses to Ask Dr. Geier – Is an MRI necessary to diagnose an ACL injury?

  1. doctor me operaron hace casi 7 meses de fractura de cadera y estoy peor que antes terapias diferentes doctors y nada me quita este ardor en la cadera por favor que puedo hacer

  2. Is an MRI necessary for a 16 year old girl with a possible cartilege tear from twisting knee twice? Would just having a Scope be more helpful?

    Appreciate your response.


    • Other surgeons might feel differently, but I usually don’t go straight into surgery unless I know that a patient has a problem that needs to be treated surgically. Surgery is never risk free, even arthroscopic surgeries.

    • MRI studies involve slices 3mm apart – or 1mm on some – to recreate images of a body part. They are highly sensitive, but they can miss occasionally injuries or show signal that appears to be an injury when it isn’t.

  3. I had lateral release on my right knee 9 months ago, the Doctor told me i should be able o continue to play softball 4 weeks later. So i waited 5 weks and went out to play. i went for a ball and heard a loud pop and was in alot of pain. had an MRI done and it was normal, but i am still haveing issues could the MRI be wrong, and i could have an ACL tear?

  4. Hi,
    I fell from my motor bike a month back. At the time of injury i just tried to stand up and move i was able to stand but when i tried walking it just didn’t support and people had to hold me back… There wasn’t any significant swelling or pain as well. Pain was way below my knee. My leg was distorted and twisted so whenever i try to walk it used to move in weird way. But now after 1 month of excersizes it seems fine. But here is the problem , I went for an MRI it reads “Full thickness tear of ACL at femoral attachment” and doctor confirmed it through positive lachman test.
    I am walking, climbing stairs even running on that leg without any problems weird it feels it is almost as good as my other leg. I went to see other surgeon after 1 month he said there is laxity but not enough to cause instability and asked me to do strengthening excersizes and see how things

    • sorry submitted bit early :)

      work out… But i am just wondering is it really torn.. My MRI 0.3 tesla and distorted leg not sure if it was really correct.I just heard if you have full thickness tear it is impossible to move around without buckling. One of the doctor has suggested for ACLR but i am confused whether to go for it or not.

      • It is possible to have a complete ACL tear but the patient doesn’t have knee instability depending on his activities and lower extremity muscle strength.

  5. Following a work-related knee injury, my daughter eventually had an MRI. The radiologist reported mucoid degeneration, cystic lesion and mentioned celery stalk appearance that is indeed visible on the films. The workmen’s comp physician stated she does not have a cystic lesion or mucoid degeneration- although while looking at the MRI films he said “is that a celery stalk”? He has recommended physical therapy and has told her she does not need surgery. Her physical therapist has told her that her limited range of motion and pain on flexion is all in her head and if she will change her attitude her condition will improve. Because the limited mobility she is experiencing could end her career before it even begins- she is a recruit in the police academy- I have researched the literature on this condition in hopes of finding support for physical therapy as a successful treatment modality. From the literature, it appears that arthroscopy is the only successful (and logical) treatment for restoring ROM in the presence of a cystic lesion. What do you think about physical therapy as a treatment for this condition?

    • I can’t say specifically in her case or about what her injury is. Generally PT can be very helpful in restoring range of motion. If a knee is stiff for a long period of time, scar tissue can develop that can make it more difficult for PT to overcome it. Surgery is often needed in many cases.

  6. Sir i fell from the bike 3 month doctor suggested mri and he found pcl avulsion with acl sprain injury.i m doing quadrite excercise.but nt very good responce.i have still swelling with instability and too much pain.plz suggest what is the proper it required surgery.

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david-headshot I am an orthopaedic surgeon and sports medicine specialist in Charleston, South Carolina.

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