A medial meniscus tear is damage to the C-shaped piece of cartilage that sits on the inner side of your knee joint, acting as a shock absorber between your thighbone and shinbone. It’s one of the most common knee injuries, affecting both young athletes who twist or pivot forcefully and older adults whose cartilage gradually wears down over time. MRI studies of middle-aged and older adults show that about 28% have a medial meniscus tear even without symptoms, and that number climbs with age, reaching over 50% in people past 80.
What the Medial Meniscus Does
Your knee has two menisci: one on the inner (medial) side and one on the outer (lateral) side. The medial meniscus is C-shaped, roughly 9 to 10 millimeters wide and 3 to 5 millimeters thick. Together, these two pads of rubbery cartilage transmit about 50% of your body’s weight when your leg is straight and up to 85% when your knee is bent. Without them, the forces passing through your knee concentrate on a much smaller area of bone and cartilage, accelerating wear.
The medial meniscus also plays a key role in knee stability. Its posterior horn (the back portion) is the main secondary stabilizer preventing your shinbone from sliding forward, which is especially important if you’ve injured your ACL. Compared to the lateral meniscus, the medial meniscus is more firmly anchored to the joint capsule and moves about half as much during knee motion. That limited mobility is part of why it tears more often: it can’t slide out of harm’s way as easily when the knee twists.
How Tears Happen
In younger people, medial meniscus tears typically result from a forceful twist or pivot while the foot is planted, common in sports like soccer, basketball, and skiing. The knee bends and rotates at the same time, trapping and tearing the cartilage. These acute tears often happen alongside other injuries, particularly ACL tears.
In people over 40, tears are more often degenerative. Years of load-bearing gradually weaken the meniscal tissue, and something as unremarkable as squatting to pick up a bag of groceries can be enough to cause a tear. Some degenerative tears develop so slowly that the knee never swells dramatically, and the person may not recall a specific injury at all.
Types of Meniscus Tears
Not all tears behave the same way, and the pattern matters for both symptoms and treatment options:
- Bucket-handle tear: A vertical tear where a flap of cartilage flips into the center of the joint, like the handle of a bucket folding over. This is the classic cause of a knee that locks and won’t fully straighten.
- Oblique or flap tear: Sometimes called a parrot-beak tear, this produces a loose flap that can catch during movement, causing intermittent clicking or locking.
- Radial tear: Runs perpendicular to the normal curve of the meniscus. When a radial tear extends all the way to the outer edge, it disrupts the meniscus’s ability to distribute load almost as severely as losing the entire structure.
- Horizontal tear: Splits the meniscus into upper and lower layers. These are more common in older adults and sometimes lead to fluid-filled cysts along the joint line.
Symptoms to Watch For
The hallmark symptoms of a medial meniscus tear are pain along the inner side of the knee and a catching or locking sensation. With an acute tear, the knee often swells within a few hours. You might be able to walk on it initially, but over the following day or two the joint stiffens and bending it fully becomes difficult.
Locking is especially telling. If a torn fragment displaces into the joint, you may find that your knee physically won’t straighten all the way, or it suddenly gives out during a step. Some people describe a “clunk” when the fragment shifts back into place. Degenerative tears without a loose fragment can still cause aching, stiffness after sitting, and pain with deep squats or twisting motions, but they’re less likely to produce that dramatic locking.
How It’s Diagnosed
A physical exam often provides strong clues. The McMurray test is a standard maneuver in which the examiner bends, straightens, and rotates your knee while feeling for a click or pain along the joint line. It’s particularly useful for detecting tears in the rear portion of the meniscus. Tenderness when pressing directly along the inner joint line is another reliable sign.
MRI is the go-to imaging study for confirming a tear and identifying its pattern, size, and location. X-rays won’t show the meniscus itself since it’s soft tissue, but they can rule out fractures or show signs of arthritis that might explain similar symptoms.
Why Blood Supply Determines Treatment
One of the most important factors in meniscus treatment is where the tear sits relative to the blood supply. Only the outermost 15% of the meniscus in adults receives blood flow. This peripheral strip is known as the “red zone.” The inner portion, the “white zone,” has essentially no blood supply.
This distinction matters because tissue needs blood to heal. Tears within the red zone, roughly within 3 to 4 millimeters of the outer rim, have a reasonable chance of healing if repaired. Tears deep in the white zone generally cannot heal on their own or even with surgical repair, which is why they’re more often trimmed away rather than stitched.
Treatment: Conservative vs. Surgical
Small tears under about 1 centimeter are typically managed without surgery. That means rest, ice, anti-inflammatory medication, and physical therapy focused on strengthening the muscles around the knee, particularly the quadriceps and hamstrings, to compensate for the lost cushioning. Many degenerative tears in older adults fall into this category, and a structured rehab program can bring significant relief even though the tear itself doesn’t fully heal.
Larger tears, those 1 centimeter or more, and tears involving the meniscal root rarely heal on their own and generally need arthroscopic surgery. The two main options are repair and partial meniscectomy (trimming).
Meniscus Repair
When the tear is in or near the red zone and has a clean pattern, the surgeon stitches the torn edges back together. Recovery is slower because the tissue needs time to heal: you’ll typically use crutches for two to four weeks and wear a knee brace for the first six weeks. Jogging usually starts around three to four months, and return to sports takes six to nine months depending on the sport and the level of play.
Partial Meniscectomy
When the tear is complex or sits in the avascular white zone, the surgeon trims away the damaged portion and smooths the remaining edges. Recovery is considerably faster. Most people can put full weight on the leg immediately, sometimes needing crutches for just the first week. Return to normal sports and activities generally happens within four to eight weeks.
There’s a tradeoff, though. Preserving as much meniscus as possible protects the joint long-term, which is why surgeons prefer repair when the tear pattern and location allow it.
Long-Term Risks of Leaving a Tear Untreated
A torn meniscus changes the way forces distribute across your knee, and over time that uneven loading accelerates cartilage breakdown. Research has found that meniscal tears on MRI are associated with roughly 2.7 times the risk of developing knee osteoarthritis. One study of nearly 1,000 people found that meniscal damage increased the risk of visible arthritic changes within just 30 months by a factor of six.
Even after partial meniscectomy, the risk isn’t zero. In a follow-up of 221 patients who had part of their meniscus trimmed, 48% showed osteoarthritic changes at 8 years and 67% at 16 years. That progression is a major reason the current approach favors repairing the meniscus whenever possible rather than removing tissue, and why physical therapy to strengthen the knee is important regardless of whether you have surgery.
Not every tear requires aggressive treatment, and many small or degenerative tears stabilize with rehab alone. But tears that cause persistent locking, catching, or swelling deserve attention, because the mechanical irritation from a loose or displaced fragment can damage the smooth cartilage surfaces that line the joint, setting the stage for arthritis years down the road.