Introduction
Knee care · ACL and meniscus injuries
ACL tear vs meniscus tear: how the two injuries differ
Dr Sean Leo · Orthopaedic Surgeon (Specialist in Orthopaedic Surgery) · Clinical Interest: Knee Conditions, Injuries & SurgeryMBBS, MRCS (Ed), MMed (Ortho), FRCSEd (Ortho)
Written by Dr Sean Leo, a consultant orthopaedic surgeon whose clinical focus is the knee, sports injuries and the lower limb.
Both can follow a twist of the knee, but they usually feel different early on. An ACL (anterior cruciate ligament) tear often brings a pop and rapid swelling, and the knee may give way. A meniscus tear more often brings joint-line pain, delayed swelling and catching or locking. Examination and, where needed, an MRI tell them apart.
Take-home: A pop, swelling, pain or a knee that catches describes an injury. It does not name it.
Dr Sean LeoOrthopaedic Surgeon, Singapore
Clinic enquiries · Not an emergency service
Illustrative image
What do the ACL and the meniscus each do
What do the ACL and the meniscus each do
What do the ACL and the meniscus each do?
The ACL is a ligament in the centre of the knee. It stops the shin bone sliding forward under the thigh bone.
The menisci are two C-shaped wedges of tough, rubbery fibrocartilage, one on each side of the knee. They share out load and absorb shock. [1]
One is a stabiliser. The other is a cushion. They are injured, and heal, by different rules.
What’s covered on this webpage
Follow the route in order, or jump to the stop you need. Stops you have read are marked.
Why does the meniscus side have two stories
Why does the meniscus side have two stories
Why does the meniscus side have two stories?
A traumatic meniscus tear follows a twist on a bent, weight-bearing knee, or a direct blow, usually in younger, active people. A degenerative lesion builds slowly in a middle-aged or older knee, often with no clear injury. [2] [3]
The evidence differs for each. A 22-year-old who twisted a planted knee and a 55-year-old whose knee slowly became painful have different problems.
How does each injury usually happen
How does each injury usually happen
How does each injury usually happen?
ACL. These tears typically happen without contact: pivoting, sudden slowing, an awkward landing or hyperextension. A pop may be felt or heard, with early swelling. A pop can be a sign, but it is not a diagnosis, and not everyone notices it.
Meniscus. A traumatic tear follows a twist on a bent, weight-bearing knee, or a direct blow. A degenerative lesion has no single moment.
Either structure can be hurt in the same event.
What does each one feel like in the first hours
What does each one feel like in the first hours
What does each one feel like in the first hours?
ACL. Swelling that comes quickly, and a knee that gives way or “cannot be trusted”, especially with twisting.
Meniscus. Pain along the joint line, catching or clicking, and swelling that may start hours to days later. True locking is a warning pattern.
The main contrast is instability (ACL) against mechanical symptoms (meniscus). Both can hurt and swell, and no single clue decides it. See also identifying an ACL tear.
ACL tear vs meniscus tear
ACL tear vs meniscus tear
ACL tear vs meniscus tear: side by side
This table describes tendencies. It cannot tell you which injury you have.
| ACL (anterior cruciate ligament) tear | Meniscus tear | |
|---|---|---|
| Typical moment | Non-contact pivot or awkward landing. | Traumatic: a twist on a bent knee. Degenerative: no single moment. |
| Sound and swelling | A pop in many, not all; swelling often quick. | No typical sound; swelling may start hours to days later. |
| What it feels like | A knee that gives way. | Joint-line pain, catching, clicking or locking. |
| Usual direction | Individualised: rehabilitation or reconstruction. | Traumatic: repair where possible. Degenerative: exercise first. |
How does a clinician tell them apart
How does a clinician tell them apart
How does a clinician tell them apart?
A clinician starts with your story, then examines the knee. These tests are not for trying at home.
- Lachman test: with the knee slightly bent, the clinician gently draws the shin forward to feel whether the ACL holds it. It is the most sensitive bedside test for an ACL injury. [4]
- Pivot-shift test: the clinician gently rotates and straightens the knee to feel the shift an ACL-deficient knee can make. It is very specific but not very sensitive, especially for partial tears. [4]
- McMurray test: the clinician bends and rotates the knee, feeling and listening for clicks or pain along the joint line. On its own its accuracy is poor to moderate. [5]
- Thessaly test: you stand on one leg and twist with the knee slightly bent. Pain or catching can suggest a tear. Pooled accuracy is moderate, and the original high figures were not reproduced. [5]
- Joint-line tenderness: the clinician presses along the joint line to find the tender spot. [5]
A normal result does not rule a tear out, and no single test settles it.
MRI shows both injuries and any damage around them, but it is used selectively. For the meniscus, ESSKA advises it when arthroscopy is being considered. [2] It adds information. It does not decide treatment alone.
Why does healing differ so much?
Why does healing differ so much?
Why does healing differ so much?
ACL. Healing is poor. Most complete tears do not heal with rehabilitation alone. In one trial’s follow-up analysis of young, active adults, a minority showed healing on MRI: 16 of 54 (30%) in the rehabilitation-first group. [6] That is an association, not proof that ACLs heal on their own.
Meniscus. Healing depends on blood supply. Only the outer rim, roughly the outer 10 to 30%, has a meaningful supply. Repair depends on a tear’s location, pattern and tissue quality. Roughly 3 in 10 tears are potentially repairable, an expert estimate, and far fewer are actually repaired. Yours may or may not be repairable. [1] [2]
Can both be torn at once?
Can both be torn at once?
Can both be torn at once?
Yes. The two often occur together, because an unstable knee loads the meniscus. In observational studies, repeated instability and longer delay before reconstruction are associated with more medial meniscus damage.
One injury can hide the other. If a knee that gives way also catches, clicks or locks, the assessment looks at both. A meniscus repair done with ACL reconstruction lengthens rehabilitation to around 9 to 12 months. [7]
How do treatment and recovery differ
How do treatment and recovery differ
How do treatment and recovery differ?
ACL. Management is individualised. In young, active, non-professional adults, structured rehabilitation with optional later reconstruction was not inferior to early reconstruction. [8] Reconstruction is the usual path for a complete tear when you want to return to pivoting sport or the knee keeps giving way.
Meniscus. For a degenerative tear, structured exercise and physiotherapy are the evidence-based first line. [9] [10] For a traumatic tear that can be repaired, preserving the meniscus is preferred. Trimming (partial meniscectomy) is aimed at true mechanical problems, such as a displaced fragment or true locking, or at care that has not worked, not as routine clean-up.
Decisions sit on the ACL reconstruction surgery and meniscus repair surgery pages.
Recovery after each, in ranges only
Your surgeon sets your timeline. After ACL reconstruction, around nine months or longer is a commonly used orientation for returning to pivoting sport, not a fixed minimum. Milestones matter more than the calendar. [11]
After a partial meniscectomy, most athletes in studies were back to pre-injury activity at about 7 to 9 weeks. After an isolated meniscus repair, athletes in studies returned to sport after an average of about 5 to 6 months. A 2024 consensus suggests waiting about 6 to 9 months (low-grade evidence). The averages describe when athletes actually returned. The consensus is a more cautious recommendation. [7] [12]
For timelines in more depth, see meniscus tear recovery time.
Losing meniscus tissue is associated with a higher risk of osteoarthritis over time. [13] The long-term trial evidence is in 10 years of evidence on keyhole surgery for wear-related meniscus tears.
When is a knee injury urgent?
When is a knee injury urgent?
When is a knee injury urgent?
Signs that need urgent help
Some symptoms should not wait for a routine appointment. Each item below says where to go.
After an injury
- The kneecap has slipped out of place and is still out, or the knee looks deformed. Go to an emergency department. If the kneecap went back into place by itself, arrange an early assessment.
- The leg looks twisted or bent, a bone is showing, there is a deep cut, or the foot or leg turns cold, pale, numb, blue or white. Go to an emergency department or call 995.
- You cannot lift your leg up with the knee kept straight, and you may feel a gap just above or just below the kneecap. Arrange an urgent same-day assessment.
At any time
- The knee is stuck and will not straighten, or it is very painful and you cannot move it or put weight on it. Arrange an urgent same-day assessment.
- The knee is suddenly very painful, hot, red and swollen, especially with a fever or feeling generally unwell. Go to an emergency department or call 995.
- One calf or thigh is newly painful and swollen. Arrange an urgent same-day assessment. If you also feel short of breath or have chest pain, call 995.
After knee surgery
- The operated knee becomes more painful, swollen or red, a wound is leaking, or you develop a fever. Contact your surgical team straight away. If you cannot reach them the same day, go to an emergency department. If you feel very unwell, go to an emergency department. If you are short of breath or have chest pain, call 995.
If you are admitted by the doctor at the urgent care centre of one of these private hospitals, the Parkway Pantai hospitals (Mount Elizabeth Orchard, Mount Elizabeth Novena, Gleneagles and Parkway East), Farrer Park Hospital and Thomson Medical Centre, you may ask for Dr Sean Leo to be your attending orthopaedic surgeon. If you are instead discharged and referred for orthopaedic follow-up, you may contact the clinic to arrange an appointment. Both are subject to the hospital’s admission processes and to Dr Leo’s availability.
Questions people often ask
Common questions
Frequently asked questions
Which is worse, an ACL tear or a meniscus tear?
Neither is simply worse. It depends on which structure is hurt, which tear pattern, and what you want the knee to do. Both are treatable.
With you through the seasonsMeet Dr Sean Leo
Meet Dr Sean Leo
A consultant orthopaedic surgeon whose clinical focus is the knee, sports injuries and the lower limb.
- Dr Sean Leo is a consultant orthopaedic surgeon. OrthoKinetics is his professional brand; clinical services are provided through OrthoSports Orthopaedic & Sports Surgery at Mount Elizabeth Novena Specialist Centre and Connexion, Farrer Park Hospital.
- His clinical interests include sports injuries, including those in adolescent athletes; ligament reconstruction; realignment surgery; cartilage repair and joint-preservation approaches; knee replacement; and technology-assisted hip and knee surgery.
- The consistent aim is to return people to meaningful function and activity while avoiding unnecessary downtime.
- Qualifications: MBBS, MRCS (Ed), MMed (Ortho), FRCSEd (Ortho).
More detail: Meet Dr Sean Leo
- Training and career: Dr Leo trained in medicine at the National University of Singapore and served in the Singapore Armed Forces Medical Corps from 2000 to 2012, where his work included the care of soldiers in physically demanding roles. He completed postgraduate orthopaedic training in 2009 and a one-year clinical fellowship at Royal North Shore Hospital in Sydney, Australia, before joining Changi General Hospital as an orthopaedic consultant in 2012, where he later held the positions of Senior Consultant and Director of the Hip and Knee Service. With seniority, his educational contribution has evolved towards mentorship and support for junior doctors.
What should I do next?
What should I do next?
What should I do next?
An assessment brings together your story, an examination and the imaging that helps. An appointment supports an informed decision. It is not a commitment to surgery.
- If your story leans ACL (a pop, rapid swelling, a knee that gives way): ACL reconstruction surgery.
- If it leans meniscus (joint-line pain, catching or locking): meniscus repair surgery.
- If you are unsure, both fit, or the knee locked: arrange an assessment.
- For another comparison, see ACL vs MCL tear.
- Browse the Knee Hub for other knee problems.
- This page provides general information and cannot diagnose an individual condition. OrthoKinetics does not provide emergency or urgent care through this webpage or its WhatsApp contact.
Sources
References
References
- Fox AJS, Bedi A, Rodeo SA. The human meniscus: a review of anatomy, function, injury, and advances in treatment. Clin Anat. 2015;28(2):269-287. PMID:25125315.
- Kopf S, et al. Management of traumatic meniscus tears: the 2019 ESSKA meniscus consensus. Knee Surg Sports Traumatol Arthrosc. 2020;28(4):1177-1194. PMID:32052121. PMCID:PMC7148286.
- Beaufils P, et al. Surgical management of degenerative meniscus lesions: the 2016 ESSKA meniscus consensus. Knee Surg Sports Traumatol Arthrosc. 2017;25(2):335-346. PMID:28210788. PMCID:PMC5331096.
- Giummarra M, et al. Efficacy of non-surgical management and functional outcomes of partial ACL tears. A systematic review of randomised trials. BMC Musculoskelet Disord. 2022;23(1):332. PMID:35395764. PMCID:PMC8991495. doi:10.1186/s12891-022-05278-w.
- Smith BE, et al. Special tests for assessing meniscal tears within the knee: a systematic review and meta-analysis. Evid Based Med. 2015;20(3):88-97. PMID:25724195.
- Filbay SR, et al. Evidence of ACL healing on MRI following ACL rupture treated with rehabilitation alone may be associated with better patient-reported outcomes: a secondary analysis from the KANON trial. Br J Sports Med. 2023;57:91-99. doi:10.1136/bjsports-2022-105473.
- Lee YS, et al. Return to sports after athletes undergo meniscal surgery: a systematic review. Clin J Sport Med. 2019;29(1):29-36. PMID:29023273.
- Frobell RB, et al. A randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med. 2010;363(4):331-342. PMID:20660401.
- Katz JN, et al. Surgery versus physical therapy for a meniscal tear and osteoarthritis. N Engl J Med. 2013;368(18):1675-1684. PMID:23506518.
- O’Connor D, et al. Arthroscopic surgery for degenerative knee disease (osteoarthritis including degenerative meniscal tears). Cochrane Database Syst Rev. 2022;3:CD014328. PMID:35238404.
- Meredith SJ, et al. Return to sport after anterior cruciate ligament injury: Panther Symposium ACL Injury Return to Sport Consensus Group. J ISAKOS. 2021;6(3):138-146. PMID:34006577.
- Prill R, et al. The formal EU-US Meniscus Rehabilitation 2024 Consensus: An ESSKA-AOSSM-AASPT initiative. Part II—Prevention, non-operative treatment and return to sport. Knee Surg Sports Traumatol Arthrosc. 2025;33(8):3014-3024. doi:10.1002/ksa.12689.
- Kalske J, et al. Arthroscopic partial meniscectomy for degenerative tear – 10-year outcomes. N Engl J Med. 2026;394(17):1757-1759. doi:10.1056/NEJMc2516079. PMID:42054686.
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