The meniscus does not get as much attention as the ACL, but meniscus tears are far more common. About 850,000 surgeries are performed in the United States each year to treat them. Many more tears are managed without surgery.
Understanding what a meniscus tear feels like - and how it differs from other knee injuries - helps you know when to wait and when to get it evaluated.
What is the meniscus?
Each knee has two C-shaped pads of cartilage that sit between the thigh bone and shin bone: the medial meniscus on the inside of the knee and the lateral meniscus on the outside. They act as shock absorbers and help distribute weight evenly across the joint.
What does a meniscus tear feel like?
The classic presentation is pain along the inner or outer edge of the knee, swelling that develops over 24-48 hours, and stiffness that makes fully straightening or bending the knee uncomfortable.
In acute tears from a sudden twist or direct blow during sports, many patients describe a popping sensation at the moment of injury. The knee may feel unstable, as though it might give out.
Degenerative tears - which develop gradually in middle-aged and older adults from the meniscus wearing thin - often present differently. There is no obvious injury event. The knee just starts aching, particularly after activity, and may swell intermittently.
A feeling that the knee is "locking" or catching - where it gets stuck at a certain angle and will not straighten smoothly - is a specific sign associated with a displaced meniscus tear. If you are experiencing true locking, see a doctor promptly. It does not always resolve on its own and can cause cartilage damage if left untreated.
How is a meniscus tear different from an ACL tear?
ACL tears are often more dramatic at the moment of injury. A pop is common, swelling is rapid and pronounced (usually filling the knee within a few hours rather than days), and the knee often feels immediately unstable - patients describe feeling like they cannot trust the joint.
Meniscus tears, by contrast, may allow continued activity. It is not unusual for athletes to finish a game after a meniscus tear. The knee hurts and swells, but the structural instability typical of ACL injuries is often absent unless there is a combined injury.
The two injuries frequently occur together, particularly in the medial meniscus and ACL combination. About 50% of ACL tears involve some degree of meniscal damage.
Can you have both a meniscus tear and an ACL tear?
Yes, and it is common enough that orthopedic surgeons routinely examine the meniscus when treating an ACL injury. An MRI will typically show both injuries when they co-exist.
How is a meniscus tear diagnosed?
Physical examination can suggest a meniscus tear - pain along the joint line with pressure or during rotational testing are useful clinical signs. But MRI is the definitive test. It shows the location, size, and type of tear, all of which affect treatment decisions.
X-rays are typically normal in isolated meniscus tears and are mainly useful for ruling out bone fractures or arthritis.
Does a meniscus tear require surgery?
Not automatically. Many meniscus tears, particularly degenerative tears in older adults, respond well to physical therapy, activity modification, and time. A 2018 study in the New England Journal of Medicine found that physical therapy produced outcomes equivalent to surgery for many patients with degenerative meniscus tears.
The tears most likely to need surgery are those causing mechanical symptoms (locking, catching), those in younger patients with acute tears in the outer portion of the meniscus where blood supply allows healing, and tears that fail to improve after 6-8 weeks of conservative treatment.
When surgery is needed, the choice is between meniscus repair (stitching the torn edges together, preferred in younger patients) and partial meniscectomy (removing the torn fragment, more common in older patients or tears where repair is not feasible). Recovery from repair is considerably longer - 4 to 6 months - compared to 4 to 8 weeks for meniscectomy.
When should you see a doctor?
See a doctor if the knee swells significantly after an injury, you experience locking or catching that prevents full straightening, pain is severe enough to limit walking, or symptoms persist for more than two weeks without improvement.
A same-day or next-day visit is worth considering if the knee feels highly unstable or if you suspect a combined ACL injury. For a sore, swollen knee without those features, waiting a few days before seeking care is reasonable.
