Part of Meniscus tear
Meniscus tear vs ACL tear or MCL sprain: telling them apart
Warning signs, and when to get help
What is different about a meniscus tear, an ACL tear and an MCL sprain?
They are three different structures and they tend to behave differently, which is why the story of the injury matters as much as where it hurts.
The meniscus is a rubbery pad of cartilage inside the joint, between the thigh bone and the shin bone. A tear in it usually gives pain and tenderness along the gap between those two bones, on one side of the knee, with swelling and stiffness, trouble bending or straightening, and sometimes a clicking or crunching feeling as the knee moves (NHS). The symptom nothing else really copies is catching or locking, because a torn flap can get in the way inside the joint.
The ACL sits in the middle of the knee and stops the shin bone sliding forward and twisting under the thigh bone. A tear usually comes with a pop or a snap, a knee that fills up within a few hours, and a feeling afterward that the joint could shift when you turn. In the clinic, most people with that story also say they had to come off straight away and could not have carried on.
The MCL is a band on the inner side, outside the joint, and it stops the knee buckling inward. The usual cause is a force on the outside of the knee pushing it inward, or a sudden change of direction, and OrthoInfo lists a pop at the time, pain, tenderness and swelling over the injured spot, and a knee that feels stiff or unstable. Doctors and physios grade it by pushing the knee gently inward and feeling how much it opens up. Because it sits outside the joint, the swelling tends to sit over the ligament rather than filling the whole knee (Vosoughi and colleagues, 2021).
Which clues actually help, and which do not?
A handful of them earn their place, and they work better together than any one does alone.
Start with how fast it swelled. A knee that fills up within a few hours of a twist suggests bleeding into the joint, which can come from a torn cruciate ligament. Swelling from a meniscus tear more often builds over a few hours to 2 or 3 days. That is why the fast kind sits on the emergency list below rather than being something to watch.
Then what you felt at the time. A loud pop with immediate swelling and a knee you could not play on points toward the ligaments. A twist that hurt in one spot and got worse over the evening points more toward the meniscus.
Next, what the knee does now. Catching or locking is inside the joint. A sense that the knee might shift or give way when you pivot is more ligamentous, though a meniscus tear can also make a knee give way.
And where you can put a finger on it. A line of soreness along the gap between the two bones fits the meniscus. A line down the inner side, above and below that gap, fits the MCL.
What does not help: how much it hurts. Some complete ligament tears settle to a dull ache within a week, and some small meniscus tears are agony on the stairs. Pain level is a poor guide to what is torn.
These three are also not the only things that get injured in a twist or a fall. A break in the top of the shin bone, a kneecap that came out and went back in, and a torn tendon just above or just below the kneecap all give swelling, pain and a leg that will not do what it is told. The torn tendon has a giveaway of its own: the knee can be straightened when somebody else moves it, but you cannot lift the straight leg off the bed or hold the knee out straight yourself. That sign is on the warning list below, because a torn tendon there is repaired rather than rehabilitated, and a late repair does worse than an early one (Elattar and colleagues, 2021).
Can a test tell you which one it is?
Not on its own, and not at home. The clinical tests have been measured and they are useful rather than conclusive.
For the meniscus, a review of 9 studies with 1,234 participants found McMurray's test picked up 61% of tears and correctly cleared 84% of knees without one, joint line tenderness managed 83% and 83%, and the Thessaly test at 20 degrees managed 75% and 87%. The authors cautioned that the studies were of poor methodological quality and disagreed with each other a good deal (Smith and colleagues, 2015).
For the ACL, a meta-analysis found the Lachman test picked up 85% of ruptures and correctly cleared 94% of intact knees, while the pivot shift test picked up only 24% of ruptures but cleared 98% of intact knees, which makes it a test that confirms rather than one that rules out (Benjaminse and colleagues, 2006). The same analysis looked at the anterior drawer, which is the one people are most likely to have seen and to try at home: it did well in knees that had been unstable for months, 92% and 91%, and not in acutely injured ones (Benjaminse and colleagues, 2006). The test easiest to copy is the one that tells you least in the first week.
Read those numbers as a reason to get examined properly rather than a reason to try the tests on yourself. A hand on a knee that is swollen and guarded tells you less than the same hand a week later, which is one reason clinicians often examine twice.
None of this can give you an all clear, and that is the part worth being clear about. Take the best figure on the page at face value: a Lachman test done by someone trained still misses roughly 1 in 7 torn ACLs, and McMurray's test misses nearly 2 in 5 meniscus tears. Those numbers came from clinicians whose findings were checked against arthroscopy or a scan, not from people testing their own knee on the sofa. So no pop at the time, swelling that has settled, pain that has faded and a knee you can walk on do not rule out a complete ACL tear or a torn meniscus. People do turn up in clinic weeks later walking comfortably on a knee with no working ACL in it. If the injury was bad enough to stop you at the time, get it examined even if it feels manageable now.
Does it matter which one it is?
A great deal, because the three go in different directions. An ACL tear in an active young person leads to a conversation about reconstruction and a long rehabilitation, which is covered on the ACL reconstruction rehab page. Most MCL sprains, including many complete ones with no other ligament damage, are managed without surgery through early movement and strengthening, which is the MCL sprain program. A degenerative meniscus tear is treated with exercise first, and the meniscus tear program is built for that, while a meniscus tear from an injury in a younger knee may be worth repairing, and repairs do better done early (Kopf and colleagues, 2020).
They also travel together. OrthoInfo notes that most severe MCL tears happen alongside a torn ACL, and that a meniscus tear can happen at the same time. An assessment is looking at the whole knee rather than ticking one box, which is why a confident self-diagnosis is the one thing not to do here.
When two of them are torn, what changes is not only the name of the injury. It is the operation and the calendar. A repairable meniscus tear found alongside a torn ACL is usually dealt with during the same operation as the reconstruction, because the ESSKA consensus puts keeping the meniscus first and advises repair as early as possible where a tear can be repaired (Kopf and colleagues, 2020). After that, the stricter set of limits is the one that counts. A stitched meniscus has to heal, so how much weight goes through the leg, how far the knee bends, and when you may squat, kneel or twist on it are usually held back further and lifted later than after a reconstruction on its own. Those limits are set by the surgeon who operated and they differ from one surgeon to the next, so nothing on this page or on our rehab pages replaces the instructions you were given after your own operation.
An MCL injury on top of either changes it again. Most MCL sprains do well without an operation, and surgery is considered for specific groups rather than being the usual route (Vosoughi and colleagues, 2021). Whether that holds for your knee depends on the grade of the MCL injury and on what else is torn with it, and so does the order of events: whether anything is reconstructed straight away, or whether the inner side is given time to heal first. That sequence is a decision for a knee surgeon who has examined and scanned the knee, and it is not something a list of symptoms can settle. A knee in which two or more ligaments have gone is treated as an injury in its own right and is assessed in hospital, with the blood supply and the nerves checked first, because it sits on the same spectrum as a knee that came out of place and went back by itself (Ockuly and colleagues, 2020; Medina and colleagues, 2014).
What should you do before you are assessed?
Treat it as an injury that has not been identified yet, because it has not.
For the first few days, the NHS advises resting the knee when you can without stopping moving it completely, then trying gentle movements after a few days. An ice pack wrapped in a towel, for up to 20 minutes every 2 to 3 hours, can ease the pain, and the NHS advises against carrying anything heavy at this stage. Never put ice on skin that cannot feel properly. Use crutches while you are limping, and keep off turning and pivoting on that leg until someone has looked at it. If nobody has fitted the crutches for you, ask a physio or a pharmacist to set the height before you rely on them, and take stairs one step at a time with a hand on the rail, because crutches at the wrong height on a staircase are their own way of getting hurt.
Get the knee seen soon rather than eventually. If the pain started with a clear twisting injury and you are young and active, book an assessment in the next few days even if it seems to be settling, and read the warning list below first, because several of the signs there need help the same day or faster. Waiting has a cost here that a settling knee hides: if the meniscus tear turns out to be one that can be stitched, the chance of stitching it is best taken early (Kopf and colleagues, 2020). If the injured knee belongs to a child or teenager, have it looked at by a doctor or physio rather than working out at home which structure it is, because a growing knee can be injured in ways an adult knee is not. If your knee pain came on gradually with no injury at all, a meniscus tear without an injury explains the degenerative pattern, and if the main thing you notice is swelling, locking or the knee letting you down, swelling, locking and giving way covers which of those is urgent. Pain you can trace along the inner joint line is also covered in inner knee pain.
Related exercise programs
Warning signs
Get emergency help now
- Emergency: the knee has moved out of place, looks misshapen or is pointing at an odd angle, or you have tingling or no feeling in the knee, leg or toes, or your foot turns cold, pale or blue. Go to an emergency department straight away. Do not drive yourself: ask someone to drive you or call an ambulance.
- Emergency: the whole knee, not just the kneecap, felt as though it slid or shifted right out of place at the moment of injury, even if it went back straight away, or the knee now feels loose or wobbly in more than one direction. Go to an emergency department straight away. Do not drive yourself: ask someone to drive you or call an ambulance. A knee that comes out of place and goes back can tear several ligaments at the same time and can damage the artery or the nerve behind the knee. That damage is not always obvious at first, and the knee can look almost normal, so it is checked in hospital on the day rather than worked out at home.
- Emergency: the knee became very swollen very quickly, within a few hours of a twist, fall or blow, or you felt a pop or snap. Go to an emergency department straight away. Do not drive yourself: ask someone to drive you or call an ambulance. Swelling from a meniscus tear often builds up more slowly, over a few hours to 2 or 3 days, and a meniscus tear from sport often comes with other damage inside the knee, such as a torn ligament (the ACL), so fast swelling needs checking.
Get help today
- Same day: the knee is locked, which means it is stuck bent and you cannot fully straighten it, even after gently trying to move it, or you cannot bend or straighten the leg at all. Get assessed the same day by a doctor, at urgent care or at an emergency department. A torn piece of meniscus can get caught in the joint and block it, and when a tear like this can be repaired, it should be done as early as possible. A knee that catches for a moment and then frees itself can happen with a meniscus tear. That is not the same as a locked knee, but tell your physio or doctor about it.
- Same day: you felt the kneecap slip out of place and it went back by itself. Get assessed the same day.
- Same day: the knee straightens when someone else moves it for you, but you cannot lift the straight leg off the bed yourself or hold the knee straight against gravity, or you can feel a gap or a dip just above or just below the kneecap. Get assessed the same day by a doctor, at urgent care or at an emergency department. The tendon that straightens the knee can tear, which is not a meniscus or a ligament problem and is not treated with exercises. It is usually repaired, and a tendon repaired late does less well than one repaired early.
- Same day: since an operation on your meniscus, the knee locks, catches or gives way again, or you feel a pop or a shift inside it, or it swells up or becomes much more painful after a twist, a kneel or a deep bend. Keep your weight off it and contact your surgical team, or get assessed the same day at urgent care or an emergency department. A repair can come apart before the tear has healed, and a trimmed meniscus can tear again. If the knee is only a little achy after a busy day, with no swelling and no catching, it is not an emergency, but tell your physio or surgeon in the next few days.
- Same day: the knee swells up with no clear reason, especially if you take medicine to thin your blood. Get medical advice the same day.
- Same day: you cannot walk or put weight on the leg, whether or not there was a fall or injury, or you have very bad knee pain after a fall or injury, or very bad knee pain that came on suddenly with no injury at all. Get medical advice the same day.
- Same day: the knee keeps giving way under you, or it gave way after a recent injury, or it gives way and is also very painful or swollen. Get medical advice the same day. If it only happens now and then, with no recent injury and no swelling, it is not an emergency, but book an assessment with a physio or doctor in the next few days. Until it has been checked, leave out the exercises you do standing on one leg, hold the rail on stairs and take care on uneven ground, because a knee that gives way without warning is how people fall.
- Same day: since your operation, your wound is oozing, leaking or has pus coming out of it, or its edges start to come apart, or your knee is tender, swollen, painful or red and it is not getting better or is getting worse, or you have a high temperature or feel hot and cold or shivery. Redness can be harder to see on brown or black skin. Contact your surgical team the same day, or get urgent medical advice if you cannot reach them. These can be signs of an infection in the wound or the knee joint. If you feel very unwell, go to an emergency department. If you have a very high or very low temperature, shivering you cannot control, you are breathing very fast or finding it hard to breathe, you are confused or your speech is slurred, your skin, lips or tongue look blue, gray, pale or blotchy (on brown or black skin this can be easier to see on the palms of the hands or soles of the feet), or you have a rash that does not fade when you press it, call emergency services, as this can be sepsis.
- Same day: the knee is hot, red and swollen, or you have knee pain with a high temperature or feel hot, cold or shivery. Get medical advice the same day, and go to an emergency department if you feel very unwell. This can be a sign of infection in the joint, which needs treatment quickly.
- Same day: a calf or thigh that is newly swollen or getting more swollen, warm, tender, red or darker than usual, has swollen veins that are sore to touch, or has a throbbing or cramping pain that does not fit your injury or condition, or that feels different from normal muscle soreness after exercise. This can be a sign of a blood clot (deep vein thrombosis), especially after surgery, an injury, time in a cast or boot, a long trip or a spell of being much less mobile than usual. Get medical advice the same day. If you are also short of breath or have chest pain, call emergency services.
- Same day: pain at night or at rest that keeps getting worse. If you are being treated for cancer now, contact your cancer team the same day.
Book an appointment
- Within a day or two: pain at night or at rest that keeps getting worse. If you have had cancer, now or in the past, see your doctor sooner, within a day or two, and mention it, even if the pain is not getting worse. Do the same if you have knee pain and are losing weight without trying, even if it does not hurt at night.
- Within a few days: pain at night or at rest that keeps getting worse. See your doctor within a few days.
Common questions
How do I know if I tore my meniscus or my ACL?
You do not, not reliably, and nor does anyone else without examining the knee. The pattern that points toward the ACL is a pop at the moment of injury, a knee that swells within a few hours, and a feeling that the joint could shift when you turn. The pattern that points toward the meniscus is pain along one side of the joint, swelling that builds over a few hours to 2 or 3 days, and catching or locking. Both can be present, because a meniscus tear from sport often comes with ACL damage. A knee that became very swollen very quickly, within a few hours of a twist, fall or blow, needs an emergency department straight away, and you should not drive yourself: ask someone to drive you or call an ambulance.
Can you have a meniscus tear and an ACL tear at the same time?
Yes, and it is common after a sports injury. OrthoInfo notes that most severe MCL tears happen together with a torn ACL, and that a meniscus tear can happen at the same time. That is one reason a knee that swells up quickly after a twist is treated as urgent rather than watched: the assessment is looking for everything that happened, not for one thing. The combination also changes what is done about it. Where the meniscus tear can be repaired it is usually repaired during the same operation as the ACL reconstruction, and the aftercare then follows the repair's limits, which are stricter and run longer than those for a reconstruction on its own. Your own surgeon sets them.
Does an MCL sprain cause locking?
Not usually. An MCL sprain is an injury to a band on the outside of the joint, so it gives a line of tenderness and swelling down the inner side rather than a joint full of fluid, and it does not put a loose fragment inside the knee. Locking and catching point inside the joint, which is meniscus territory. A knee that is stuck bent and will not straighten needs assessing the same day. A knee that catches for a moment and then frees itself is not the same thing, but tell your physio or doctor about it. If you cannot tell which of the two you have, treat it as the same-day one.
Do I need an MRI to tell a meniscus tear from an ACL tear?
Sometimes, and it depends on your age and how it happened. For middle-aged and older people with knee pain, the ESSKA consensus says MRI is usually not needed as a first step and that a weight-bearing X-ray is the first scan to use (Beaufils and colleagues, 2017). After an injury in a younger knee, ESSKA says the decision about MRI should be made by a musculoskeletal specialist when arthroscopy is being considered (Kopf and colleagues, 2020). So the scan follows the assessment rather than replacing it.
What should I do in the first few days while I wait to be seen?
The NHS advises stopping exercise and resting the knee when you can in the first few days, without stopping moving it completely, and trying gentle movement after a few days. An ice pack wrapped in a towel, for up to 20 minutes every 2 to 3 hours, can ease the pain, and the NHS also advises against carrying anything heavy at this stage. Never put ice on skin that cannot feel properly. Use crutches if you are limping, and avoid turning on the injured leg. Get the crutch height set by a physio or pharmacist rather than guessing it, and take stairs one step at a time holding the rail. If you cannot walk or put weight on the leg, get medical advice the same day.
References
- Smith BE, Thacker D, Crewesmith A, Hall M. Special tests for assessing meniscal tears within the knee: a systematic review and meta-analysis. Evidence Based Medicine. 2015;20(3):88-97. https://doi.org/10.1136/ebmed-2014-110160
- Benjaminse A, Gokeler A, van der Schans CP. Clinical diagnosis of an anterior cruciate ligament rupture: a meta-analysis. Journal of Orthopaedic and Sports Physical Therapy. 2006;36(5):267-288. https://doi.org/10.2519/jospt.2006.2011
- Kopf S, Beaufils P, Hirschmann MT, et al. Management of traumatic meniscus tears: the 2019 ESSKA meniscus consensus. Knee Surgery, Sports Traumatology, Arthroscopy. 2020;28(4):1177-1194. https://doi.org/10.1007/s00167-020-05847-3
- Beaufils P, Becker R, Kopf S, et al. Surgical management of degenerative meniscus lesions: the 2016 ESSKA meniscus consensus. Knee Surgery, Sports Traumatology, Arthroscopy. 2017;25(2):335-346. https://doi.org/10.1007/s00167-016-4407-4
- Vosoughi F, Rezaei Dogahe R, Nuri A, Ayati Firoozabadi M, Mortazavi J. Medial collateral ligament injury of the knee: a review on current concept and management. Archives of Bone and Joint Surgery. 2021;9(3):255-262. https://doi.org/10.22038/abjs.2021.48458.2401
- Ockuly AC, Imada AO, Richter DL, Treme GP, Wascher DC, Schenck RC Jr. Initial Evaluation and Classification of Knee Dislocations. Sports Medicine and Arthroscopy Review. 2020;28(3):87-93. https://doi.org/10.1097/JSA.0000000000000271
- Medina O, Arom GA, Yeranosian MG, Petrigliano FA, McAllister DR. Vascular and nerve injury after knee dislocation: a systematic review. Clinical Orthopaedics and Related Research. 2014;472(9):2621-2629. https://doi.org/10.1007/s11999-014-3511-3
- Elattar O, McBeth Z, Curry EJ, Parisien RL, Galvin JW, Li X. Management of Chronic Quadriceps Tendon Rupture: A Critical Analysis Review. JBJS Reviews. 2021;9(5):e20.00096. https://doi.org/10.2106/JBJS.RVW.20.00096
- NHS. Meniscus tear (knee cartilage damage). Page last reviewed 2 September 2026. https://www.nhs.uk/conditions/meniscus-tear/
- NHS. Knee pain. Page last reviewed 21 December 2023. https://www.nhs.uk/symptoms/knee-pain/
- American Academy of Orthopaedic Surgeons. Meniscus Tears. OrthoInfo. https://www.orthoinfo.org/en/diseases--conditions/meniscus-tears/
- American Academy of Orthopaedic Surgeons. Collateral Ligament Injuries. OrthoInfo. https://www.orthoinfo.org/en/diseases--conditions/collateral-ligament-injuries/
- American Academy of Orthopaedic Surgeons. ACL injury: does it require surgery? OrthoInfo. https://www.orthoinfo.org/en/treatment/acl-injury-does-it-require-surgery/
Written and checked by the PocketPhysio editorial team. Last updated 2026-10-16.
This page is general education, not a diagnosis or a personal treatment plan. See a physiotherapist or doctor for advice about your own situation.