What a meniscus does and how it tears acutely

Inside each knee, two crescent-shaped pads of fibrocartilage — the menisci — sit between the thigh bone (femur) and the shin bone (tibia). Their job is to cushion impact, distribute load evenly across the joint surface, and help stabilise the knee through movement. Without them, force concentrates on the articular cartilage in a way the joint cannot sustain over time.

Acute tears almost always follow the same mechanical story: the foot is planted, the knee is bent, and the body rotates over it — a direction change on the football pitch, a landing from a jump, a sudden twist on uneven ground. That combination of compression and rotation is enough to split the fibrocartilage. The medial (inner) meniscus tears more frequently than the lateral, accounting for roughly 87% of tears in surgical series, partly because it is less mobile and more tightly tethered to the joint capsule.

It is worth distinguishing this from a degenerative tear, which can happen with something as unremarkable as an awkward twist rising from a chair in an older adult and follows a different clinical pathway. Acute tears are also commonly accompanied by an ACL rupture — a combination that changes both the urgency of assessment and the surgical decision-making — which is one reason a clinical examination matters far more than self-diagnosis alone.

Symptoms that suggest a meniscus tear

Recognising a meniscus tear from symptoms alone is not straightforward, but several features point clearly in that direction.

The pain typically sits at the joint line — the narrow crease along the inner or outer edge of the knee — rather than being diffuse or centred on the kneecap. At the moment of injury, many people feel or hear a distinct 'pop', though its absence does not rule out a tear.

Two misconceptions are worth correcting early:

• Delayed swelling does not mean a minor injury. The knee can look almost normal in the first hour or two. Stiffness and swelling often build gradually over 24 to 72 hours as fluid accumulates in the joint. Judging severity by how the knee looks immediately after the injury frequently leads to it being dismissed.
• Walking afterwards is not reassurance. Most people with a freshly torn meniscus can still walk, and some athletes initially continue playing. The ability to bear weight does not indicate that the meniscus is intact.

Beyond pain and swelling, two types of symptom are particularly significant. A catching or clicking sensation during movement — or a locked knee that cannot be fully straightened — suggests a displaced fragment of torn tissue interfering with joint mechanics. The knee giving way under load points to instability, which may involve a co-existing ligament injury.

None of these features individually confirms a tear; together, they make a strong case for proper clinical assessment rather than watchful waiting.

What to do in the first 48–72 hours

If the knee is not locked and you can bear some weight, the priority in the first 48–72 hours is straightforward: protect the joint, reduce swelling, and monitor closely for any change that needs urgent attention.

• Rest the knee — stop the activity that caused the injury and avoid anything that provokes pain or instability. Gentle movement within a pain-free range is fine; forced loading is not.
• Apply ice wrapped in a cloth or tea towel for 15–20 minutes several times a day. Do not place ice directly against skin.
• Compress with a bandage and elevate the leg above hip height when resting — both help limit the fluid accumulation in the joint that drives swelling and pain.
• Over-the-counter analgesia — paracetamol, or ibuprofen if you tolerate anti-inflammatories — is appropriate for pain in the acute phase.

This approach buys time for the acute inflammation to settle; it is not a substitute for assessment. Keep a close watch on how the knee behaves. If it locks and will not fully straighten, if you cannot bear any weight, or if swelling worsens rapidly, do not continue with self-care — move directly to seeking urgent specialist review, as covered in the next section.

For a knee that is already locked at the time of injury, skip this section entirely.

When to seek urgent help

The locked knee is the clearest signal that something beyond a stable tear has occurred. When a fragment of torn meniscus — most commonly in a bucket-handle pattern — displaces into the joint, it physically blocks full extension. The knee becomes mechanically stuck, typically 10–30 degrees short of straight. This is not stiffness or guarding; the joint genuinely cannot be extended, even gently. A locked knee warrants same-day orthopaedic review. Left unreduced, the displaced fragment places abnormal pressure on joint surfaces and can cause osteochondral damage — injury to cartilage and the underlying bone — that is far harder to address than the original tear.

Other signs that call for urgent rather than watchful assessment include:

• Complete inability to bear weight, especially when accompanied by rapid joint swelling, suggests more significant structural disruption than a stable tear alone produces.
• Rapidly expanding swelling within the first hour or two may indicate haemarthrosis — blood filling the joint cavity. This degree of swelling raises the possibility of a concurrent ligament injury, such as an ACL rupture, which changes both the urgency and the management pathway.
• Mechanical symptoms — catching, giving way, or intermittent locking — that persist beyond 48–72 hours of conservative care suggest a tear pattern unlikely to settle without specialist input.

The clinical case for acting without delay, rather than waiting for a routine appointment, is that some tear configurations are time-sensitive from a repair-versus-meniscectomy standpoint. The longer a displaced or complex tear remains unassessed, the narrower the window in which tissue-preserving options remain viable. A specialist assessment — with clinical examination and, where indicated, MRI — is the only way to determine which pathway applies.

What a specialist assessment involves

The appointment typically follows a logical sequence — history, examination, then imaging — with each step narrowing the picture before any treatment decision is made.

A structured history comes first. The specialist will ask about the mechanism of injury, whether a pop was felt, how quickly swelling developed, and whether the knee has locked or given way since. Previous knee problems or earlier injuries to the same joint are relevant context.

Examination follows. Joint-line palpation — pressing along the inner or outer edge of the knee — can reproduce pain directly over the site of a tear. Clinical tests such as the McMurray, Apley, and Thessaly manoeuvres help detect mechanical disruption; in one comparative study, the Thessaly test correctly identified 78 of 86 confirmed cases. These tests improve diagnostic confidence but cannot determine tear pattern or location on their own.

MRI is arranged before any treatment decision. It shows the tear's size, pattern, and — critically — its position within the meniscus. Tears in the outer vascular zone, where blood supply is sufficient to support healing, are candidates for repair; tears in the inner avascular zone more often require partial meniscectomy. AI-assisted MRI analysis, part of the assessment workflow at MSK Doctors sites, can add further detail on meniscal and cartilage segmentation to inform the surgical planning discussion.

One caution applies particularly to older adults: meniscal signal change on MRI is common in people who have no significant symptoms. The specialist interprets imaging alongside the full clinical picture — an MRI finding in isolation does not confirm a symptomatic acute tear, and the two must be reconciled before a management pathway is agreed.

Treatment options and why acting quickly matters

Specialist review does not automatically lead to surgery. Many acute tears — particularly small, stable tears at the outer vascular rim of the meniscus — respond well to structured physiotherapy, load management, and a graduated return to activity. This conservative pathway is appropriate where mechanical symptoms are absent and the tear is not causing the joint to lock or give way.

When surgery is needed, the central question is whether the torn tissue can be repaired or whether some must be removed. Meniscal repair, using sutures to reattach the fragment, preserves native tissue and the joint's load-distributing capacity. This distinction has long-term significance: in published series, arthroscopic partial meniscectomy was associated with a 13.5% incidence of knee osteoarthritis within five years — a substantially higher rate than following repair. For eligible patients with acute traumatic tears presenting within approximately six weeks of injury, repair is the preferred surgical option.

Repairability depends on several factors that only a specialist can determine: tear location (outer vascular zone versus inner avascular zone), tear pattern, size, patient age, BMI, and activity level. A displaced bucket-handle tear and a small radial tear carry very different surgical options, even at the same point after injury.

Where repair is not feasible, arthroscopic partial meniscectomy remains appropriate — but it permanently removes meniscal tissue that cannot subsequently be restored. Understanding this trade-off is part of why early specialist review matters: the sooner a tear is properly assessed, the more options remain genuinely available.

For patients in Lincolnshire and the surrounding area, Lincolnshire Knee — part of the MSK Doctors group — accepts patients without a GP referral; appointments are available at Sleaford (NG34) and Grantham (NG31) at lincolnshireknee.co.uk. The broader principle applies to any patient: a reparable tear identified early stays reparable.

1. [1] Comparative Diagnostic Accuracy of MRI and Ultrasound in Meniscal Tear Detection. (2025). https://doi.org/10.1155/rrp/6270476 https://doi.org/10.1155/rrp/6270476
2. [2] Comparison of Accuracy in Expert Clinical Examination versus MRI and Arthroscopic Exam in Diagnosis of Meniscal Tear. (2020). https://doi.org/10.1155/2020/1895852 https://doi.org/10.1155/2020/1895852
3. [3] Meniscus tear. https://en.wikipedia.org/?curid=15435205 https://en.wikipedia.org/?curid=15435205
4. [4] Unlock the Knee: Utility of OMT for Acute Locked Knee Syndrome. (2025). https://doi.org/10.70709/d7h5fgjys https://doi.org/10.70709/d7h5fgjys
5. [5] High failure rate in meniscal repair when preceding ACL reconstruction. (2025). https://doi.org/10.1002/ksa.12593 https://doi.org/10.1002/ksa.12593