7 signs your knee injury could be serious

Knee injuries are among the most common injuries in sports and exercise. Fortunately, among the patients I see in the office, most knee injuries do not require surgery.

If you suffer a knee injury, how can you know if it is serious and worth seeing an orthopaedic surgeon? This list is far from comprehensive, but here are seven signs you have a knee injury that might require surgery.

It goes without saying that the information in this post, like all of my content on this blog, on my podcast, and in social media, is not intended to provide specific medical advice. Please consult your doctor for any medical concerns.

Your knee is swollen.

It might not be a big deal for your knee to have a small amount of fluid present. On the other hand, if your knee swells up like a basketball in the first few hours after an injury, you could have an ACL tear or fracture.

You heard a pop.

I don’t mean a small pop like the one you feel when you crack your knuckles. I’m also not talking about the popping many of you feel under your kneecaps normally with knee motion. If you hear or feel a loud, painful pop during an awkward landing or when you get hit in the knee, you could have torn a ligament. Many athletes say that their teammates heard the pop when they tore their ACLs.

You can’t bear weight.

Knee injury in soccerExtreme pain trying to walk is somewhat of a generic complaint. Many injuries can be serious enough to cause pain when you try to put pressure on the injured leg. It is still a sign you might consider seeking medical attention.

Your knee buckled or gave way.

If your knee buckled when you landed from a jump or changed direction suddenly, you could have suffered ligament damage, such as an ACL tear. Alternatively, if you experience your knee giving out with twisting or landing movements in sports weeks or months after an injury, you should consider seeing a sports medicine doctor. True knee instability with activities can risk further damage to the meniscus or articular cartilage.

Your knee is locked.

Younger athletes can often tear the meniscus in such away that the inner, torn fragment can flip into the center of the knee and block motion. These bucket-handle meniscus tears often require surgery. The surgeon must push the meniscus back into place and repair it with sutures or anchors. Milder or more chronic forms of knee locking or catching also can suggest you have a meniscus tear.

You cannot fully extend the knee.

Pain, swelling, and inflammation after acute injuries can all make knee range of motion difficult. If a patient comes to my office days after an injury and I can’t straighten the knee, I get at least a little concerned. It can be a nonspecific finding, though. Regardless, I have often found ACL tears, acute meniscus tears, patellar dislocations, and more in these circumstances.

Your knee hurts in a very specific location.

Patients with meniscus tears usually complain of pain in a very specific spot along the joint line rather than throughout the knee. Medial meniscus tears often hurt along the medial (inside) and posterior (back) side of the knee. Lateral meniscus tears often cause pain along the lateral (outside) and posterior aspect of the knee. Likewise, stress fractures usually cause localized pain on the bone at the site of the fracture.

I hope that this list is helpful. Again, it is not comprehensive and not intended to replace the advice of your doctor. If anything, I hope you would consider seeing your doctor sooner after injury if you have any of these complaints.

Sports medicine professionals – athletic trainers, physical therapists, and orthopaedic surgeons – are there any other findings you would add?

21 Responses to 7 signs your knee injury could be serious

  1. I was diagnosed with a sprained knee never got better had an MRI the day after I felt a pop and very painful

  2. Hello,
    I severely dislocated my knee cap six weeks ago. I have been walking on it for two weeks and making huge progress. However, I am not able to completely straighten my leg. The MRI showed no meniscus/ACL issue. I am in physical therapy however my leg just won’t straighten. What could this possibly be? I am very concerned and worried.

    • Without being involved and examining you, I can’t say if there is some mechanical block to extension, like a meniscal tear. Generally though, the lack of full extension of the knee could be serious. An orthopaedic surgeon can perform an exam and order an MRI if needed to find the problem.

  3. A day ago i was running and i fell right on my knee iits red and i can bearly straighten my knee and im just laying doown its really hurting for no reason i can even reall walk right

  4. I am going to try to summarize. A ski injury created partial tears in all ligaments in my right knee except meniscus. Had a mri and determined to be an extreme knee injury by an orthopedic surgeon Fast forward several years and I now get short periodic pain and failure to be able to fully extend leg. This pain is severe and last less then a day until I feel a pop or release. Immediately there is total relief of pain and a knee that is as normal as can be.
    I still ski, golf, hike and bike on a regular basis. Hard to get examined because it disappears.
    your best guess?

    • Without really being able to examine you and determine where in your knee the pop was coming from, I’m not sure I can point you in any particular direction. Sorry!

  5. In 2011 i triped and fell whilst out running on a pavent stone,and went down on my right knee,i went to the hospital they xrayed it and said there was nothing wrong with it,just bruised,Well several weeks later i was in the shower,and found when i put hot water on my left leg below knee i could feel it,But when i did the right it was totally knumb,I then got severe back ache and the hospital did a mri scan,to find my l3 l4 nerves were trapped in my spine,since 2011 ive had an operation on my spine and an operation on my knee,Could you tell me would this be the result of me falling and landing on my knee in 2011,at that time i was 52,im now 55,and disabled,need to wear knee brace without knee collapes,thank you,neil horne,huddersfield,uk.

    • I can’t say without examining you and looking at x-rays and an MRI. A patient with buckling or giving way of the knee might consider seeing an orthopaedic surgeon to see if any ligamentous injury exists.

  6. A person twisted my leg the wrong direction and my knee popped out I have had x ray and everything is still in tact but for the life of me I cannot bend my leg can’t force it either with hand what could be up with that?

    • Without examining you, I can’t really say. It is possible for a patient to have a mechanical block to motion (such as a loose body). An orthopaedic surgeon could deteremine if one exists and what it could be.

  7. long history with left knee…
    Medial tibial plateau fracture 7 years ago (I was 32 at the time), Schatzker 4 variant w/popliteal involvement. Several surgeries later, including fem-pop bypass & lateral uni-compartmental knee replacement.
    fast forward to current – we moved out of state, and can’t find an orthopedic surgeon to take my case (0 for 5). I’m “too high risk” because of the bypass, and I’m “too young” for even the uni-replacement – let alone consider doing anything further.
    The medial side of knee joint hurts sharply with any weight bearing, and I particularly can’t straighten it while standing/walking. It sorta feels like I’m culturing a pearl in there (If I had to imagine what an oyster goes through!), and it feels like my kneecap is grinding against sandpaper.
    Can’t feel anything on the lateral side – but then again, I have a hunk of metal on that side from the uni.

    ..without examining, of course, is this something that I simply have to live with? or should I start throwing darts at the orthopedic section phone book again?

    • I understand your frustration, but without being able to examine your knee and review studies, I can’t give you any specific answers to your questions. You might try the AOSSM website and use its Find a Doctor tool to find an orthopaedic surgeon in your area.

  8. I have had a history with my left knee, however at volleyball I jumped and heard and felt 2 pops, painful but I continued to play as I tolerate pain well. What are your suggestions?
    Please and thanks

  9. hi my name is adelaide burling i am 22 year old and i have a most common left knee injury and what happen was that i did my acl and i buckled my postier ligament it gotten to the point where i have joint effusion and plus the swelling of my left knee as been increasing and i have not been able to been able to get a opporation done yet due to western health footscray hospital recieptionist said to me it could weeks or longer so i had no choice and when it was july i found that i am pregnant and plus it stuffed up my chances of having my left knee injury done so i have to wait until the baby comes by next year though .

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

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