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.

37 Responses to 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.

  7. I got injured at work and after my MRI the doctor said I had a strained MCL and a partial tear in my ACL but said the ACL injury was from a previous incident… my question is can a doctor tell how long ago an injury occured with an MRI? It’s been 2 months since my injury and I just had my MRI 2 weeks ago.

    • I can’t know in your case without seeing it, but in acute ACL injuries, you often see a bone bruise from the event. You also see fluid within the knee.

  8. I came across your article on torn acl when I was trying to find out if you can tell if you have a torn acl with out an MRI because my boyfriend was in a motorcycle accident recently and is still recovering in a coma like state still not talking and I’m worried he may have a torn acl in his right leg since he had a compound fracture of both lower limbs and they couldn’t do an MRI on his brain because of what they used to cut the blood supply on his spleen. I know from working in an animal field we would put them under anesthetic and look for a drawer sign.
    Is there anyway to tell since he us unable to speak right now… There is fluid in the knee and it does get stiff and I think he locks it when hes awake
    Thanks for your help

  9. Hi doc, I fell down when playing football. After that, I went to the Orthopaedic surgeons and my doctor did the Lachman test, anterior drawer test and pivot test. The results are negative. But he suggested me to do an MRI to determine whether is there a meniscus tear or not. After the MRI results came out, the impression of the radiologist stated that i have a total tear of ACL and my doctor suggested for surgery. However, I went to another orthopaedic surgeons and told him the same thing to get a second opinion. He also did a third test Lachman, anterior, and pivot. The results were also negative, then he told me to do a high jump and I can do it and also i could do single leg squat using my injured knee. After that, he read my MRI results and say that this is only an ACL sprain/ partial tear grade 1. What I want to ask : is it possible when the results of MRI declared total ACL tear meanwhile the clinical/physical tests states negative.
    Thank you

  10. Hi,

    I am living in New Zealand. When I was 17 I landed on my left leg while jumping over an obstacle and hyperextended it. At the time I felt like it had dislocated. I remember clearly that there was a loud crack/pop, I collapse and could not weight bear or extend my knee due to lots of immediate swelling, I could barely move due to intense pain.

    I went to a small local Accident and Emergency where I had negative X-rays to rule out a fracture and then laughing gas was used to put me in an extension splint. I was sent home with GP follow up in 2 weeks. The GP did some ligament stability tests and did not seem concerned, then I saw a physio who was not particularly useful. I got back to walking and jogging but had infrequent discomfort.

    3 years later I went backpacking with 17kg pack and poor footwear for 8 weeks. I developed swelling, and limping, came back to NZ and saw a physio, was referred for MRI and my PCL was completely torn Grade 3 which required a surgical repair and I already had signs of osteoarthritis with osteophytes in the medial compartment and a full thickness chrondal fissure (I was only 20 years old at this time)

    I am fully convinced that I at least had a parrtial PCL tear and chrondral damage when I injured myself age 17 which remained undiagnosed due to lack of imaging and not seeing a specialist. I have subsequently graduated from medical school. I have not had a fantastic outcome post surgical repair and my arthritis is now symptomatic, the extent to which my knee effects my life really gets me down as I am only 24 with the knee of an 80 year old. I frequently reflect on the lack of MRI after the initial injury as some rehab and prevention could have been initiated back then. I know now that the history I gave my doctors was typical of significant intracapsular injury and probable cruciate ligament damage.

    My question is this: in your opinion and experience would it be standard to arrange an MRI after the acute swelling had settled based purely on my history from the first event?

    Thanks so much for your time

    • I don’t know the perspective of New Zealand’s orthopaedic surgeons. If I’m worried about multiple ligaments being injured or I’m uncertain of the extent of the injury, I often order an MRI early after an injury.

  11. I went to phisio and I’ve done my MCL. He’s a bit worried about my ACL but I didn’t hear a pop or anything when it happened. And I can actually jump up and down on it without it hurting and it feels stable. I wouldn’t be able to do that and feel stable if it I did have a tear in my ACL right ?

  12. Hello Dr.,

    Have you ever had a false positive “Full ACL Disruption” on a MRI test that was found to be incorrect?

    Thank you,


    • I can’t say that I have, but it is only one piece of information with the history of injury, physical exam, etc.

  13. My 7 year old recently suffered a knee injury. ER radiologist originally said avulsion fracture, we saw an orthopaedic doctor, where he said it was an acl tear. At the time she still had a large effusion, could not straighten the leg all the way, and had a positive lachman test even with some guarding. Initially the injury was severely painful, all activity stopped, and swelling immediately began to occur. Anyways, the doctor, who suspected ACL involvement, sent her for an MRI. I was called a few days later and told her ACL was partially torn, so we seen another orthopaedic doctor today. Surprisingly I was told by him that her ACL is fine! He says bone bruise, with a little “gray area” on the ACL while this seems like great news,I’m reluctant to believe it. She has some instability too, which leads me to further reluctance of believing her ACL is “okay”. He said she can return to all activities and ditch the brace, and that worries me! I’m thinking of another opinion. Your thoughts would be greatly appreciated! Thanks in advance.

  14. I met with a Grade 3 tear of anterior cruciate Ligament with marrow edema
    and bone micro fractions
    Joint effusion
    Grade 1 anterior horn of lateral meniscus.
    my age is 21(M) name raghu

    Do i have to go for reconstruction surgery can please tell me how many dates will it take for me to heal if went through a surgery

    and also i want to know which is better way weather going through surgery or rehabilitation process of physiotherapy

  15. My 16 year old daughter hurt her knee in P.E. about a week and half ago. She and another student collided. She did not fall, but her knee was hurt. The inside of her knee is swollen and is tender. She walks on it. She complains that it hurts to straighten. Is it possible that it is more than just a contusion? Does she need an MRI?

  16. I had a ski accident 10 weeks ago and according to the consultants and my physio they believe I have damaged my ACL and MCL. I have been booked in for an MRI scan next week, to rule out any further damage and to see how it is heeling. Would they be able to see damage to the ligaments still on the scan to confirm thats what was wrong- although it happened so long ago?? thank you 🙂

  17. i had a bike accident 3 weeks back after which i did an mri revealing both ligaments patial tear, doctor has suggested a scopy to determine the ligament damage, but is a scopy needed after an MRi. I can walk easily but cannot easily climb or run

    • Generally I think seeing a PT first can be helpful to regain motion and strength. If the PT is concerned for a patient’s knee, they can recommend seeing an orthopaedic surgeon.

  18. When a orthopedic says he “can’t find” my ACL, ordered an MRI, but prescribed PT prior to MRI. Is this a normal occurrence? He wants me in a brace 24/7, should I be taking more precautions than just the brace if my ACL is missing….

  19. Hi,

    I dislocated my knee about a week ago and the paramedics suspected ligament damage because of the severe pain I was in. I have been back for appointments 3 times since and neither of the doctors who have treated me have given me any definite answers as to whether I have ligament damage. Reading up on this online I see that ligament damage is diagnosed with an MRI but this has not once been mentioned to me. I am still in extreme pain and cannot put weight on or bend my leg.

    Do you think it would be wise to keep pushing for a diagnosis or to just let things play out and see if it still hurts in a couple of weeks?

  20. Hi doctor I’ve had pain in my upper back where my riibs are on both sides and also in my both sides like towards the serratus muscle area. When I raise my shoulders I can hear my ribs grinding/snapping sounds. It’s been 4 months and my doctor is baffled I had normal X-ray and seen physio but it didn’t help. What could this be & would a CT scan be useful? I really don’t like MRI as I am very claustrophobic.

  21. sir,I suffered a grade 1 acl injury 15 days ago…I hv to go to my army training after 24 days..the pain in my outer knee is almost gone..but there some pain in the inner side of the knee….please tell me if I can get completely fit in 24 days. thankyou

  22. Hi dr.geier
    Im mohammad and living in iran
    My mri research show acl completely torn
    But have no pain in my knee except i cant run or walking on ramp for long time
    Is it possible ?

    dr completely confused
    some of them suggested me to surgery

  23. Hello Doctor Geier.
    I have a ACL question that you can hopefully help me with. I was in a car accident previous and had knee pain and instability right away. living in Canada it took a year to have surgery on the knee. My surgeon repaired a torn miniscus and told me he also saw my ACL was partially torn. He commented that it was torn before the accident. My question: is there any way that a year after an injury to a ACL is it possible to determine that it was torn previous to that time by just looking at it in surgery?

    Thanks Doctor

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