The meniscus is a C-shaped piece of cartilage that sits inside your knee joint, acting as a cushion between your thighbone and shinbone. You actually have two in each knee: a medial meniscus on the inner side and a lateral meniscus on the outer side. Together, they absorb shock, distribute your body weight evenly across the joint, and protect the smooth cartilage coating your bones from wearing down over time. Meniscus tears are one of the most common knee injuries, occurring at a rate of about 61 per 100,000 people in the general population.
What the Meniscus Does in Your Knee
Both menisci are roughly wedge-shaped and semicircular, but they differ in size and coverage. The medial meniscus is longer (about 40 to 45 mm) and covers roughly 51 to 74% of the inner tibial plateau, the flat top of your shinbone. The lateral meniscus is shorter but covers more surface area on the outer side, about 75 to 93% of the plateau. The lateral meniscus also varies more in shape, thickness, and mobility from person to person.
The primary job of these structures is load distribution. The medial meniscus bears about 50% of the load passing through the inner compartment of the knee, while the lateral meniscus handles roughly 70% on the outer side. Without them, the full force of every step would concentrate on a small area of bone and cartilage, accelerating wear. This is why losing meniscal tissue significantly raises the risk of developing arthritis later on.
Blood Supply and Healing Zones
One of the most important things about the meniscus is that it doesn’t heal equally everywhere. Its blood supply decreases as you move from the outer edge toward the center of the knee. Surgeons divide it into three zones based on vascularity:
- Red-red zone: The outer third, with good blood flow. Tears here have the best chance of healing on their own or after surgical repair.
- Red-white zone: The middle third, with limited blood supply. Healing is possible but less predictable.
- White-white zone: The inner third, with essentially no blood supply. Tears in this region heal poorly, which makes them the most challenging to treat.
This vascular map is a major factor in deciding whether a tear can be repaired or whether damaged tissue needs to be trimmed away.
How Meniscus Tears Happen
Meniscus tears generally fall into two categories: traumatic and degenerative. Traumatic tears tend to happen in younger, active people during movements that forcefully twist or rotate the knee while bearing weight. Planting your foot and pivoting, deep squatting under load, or a direct blow during contact sports can all cause the meniscus to tear. Active-duty military personnel, for example, experience tears at a rate of 8.7 per 1,000, far higher than the general population.
Degenerative tears develop gradually as the meniscus weakens with age. The tissue becomes more brittle over time, and even something as minor as an awkward step or getting up from a chair can cause a tear that’s been brewing for years. These tears are especially common in the medial meniscus of older adults.
Types of Meniscus Tears
Not all tears look the same, and the pattern matters for treatment decisions. The main types include:
- Radial tears: These run perpendicular to the curved fibers of the meniscus, cutting across them like slicing into a crescent roll from the inside edge outward. They disrupt the meniscus’s ability to distribute load and increase joint contact pressure significantly.
- Horizontal tears: These split the meniscus into upper and lower layers, running parallel to the tibial plateau.
- Vertical/longitudinal tears: These run along the length of the meniscus, following its natural curve.
- Bucket-handle tears: A severe form of longitudinal tear where a large flap displaces into the center of the joint, often causing the knee to lock.
- Flap tears: A portion of torn tissue folds over on itself, sometimes catching during movement.
- Degenerative (complex) tears: Irregular, frayed tears in multiple directions, typically seen in older or worn-out menisci.
Symptoms of a Torn Meniscus
A torn meniscus doesn’t always announce itself immediately. With smaller tears, pain and swelling may take 24 hours or more to develop. The most common symptoms include swelling or stiffness, pain that worsens when twisting or rotating the knee, difficulty fully straightening the leg, a feeling that the knee is locked in place, and a sensation of the knee giving way. Some people also report a popping sensation at the time of injury.
Mechanical symptoms like catching and locking are particularly telling. If a loose flap of torn cartilage gets caught between the bones during movement, it can physically block the joint from moving through its full range. This is more common with bucket-handle and flap tears.
How a Meniscus Tear Is Diagnosed
Doctors use a combination of physical examination and imaging. During the exam, several hands-on tests help narrow down the diagnosis. Joint line tenderness, where the doctor presses along the seam of the knee joint, has the highest diagnostic accuracy: about 81% for medial meniscus tears and 90% for lateral tears. The McMurray test, which involves rotating and extending the knee to produce a click, is less reliable at 57% and 77% accuracy for medial and lateral tears respectively. An MRI is typically used to confirm the tear’s location, size, and type before making treatment decisions.
Treatment: Conservative vs. Surgical
Not every meniscus tear requires surgery. Small, stable tears in the outer vascularized zone can often heal with rest, ice, anti-inflammatory measures, and physical therapy. The decision to operate depends on several factors: tear size (generally between 1 and 4 cm for repair candidates), tear location and pattern, whether the tear is in the blood-rich zone, patient age (under 40 favors repair), how recently the injury occurred (less than six weeks is considered acute), and whether there’s a concurrent ligament injury like an ACL tear.
Degenerative tears in older adults frequently respond to conservative management. Younger patients with acute, vertical tears in well-vascularized tissue are the best candidates for surgical repair.
Surgical Options and Recovery
When surgery is needed, there are two main approaches. A partial meniscectomy trims away the damaged tissue, while a meniscus repair stitches the torn pieces back together. Repair preserves the tissue and produces better long-term outcomes, with lower rates of secondary arthritis (about 10% at ten years compared to 17% after meniscectomy). However, repair carries a higher reoperation rate of roughly 20.7% versus 3.9% for meniscectomy, largely because repaired tissue sometimes fails to heal.
Recovery timelines differ substantially between the two procedures. After a meniscectomy, most people can bear full weight immediately or within a few days, and return to sports in four to eight weeks. Meniscus repair requires a more cautious approach: two to four weeks on crutches, a knee brace for six to eight weeks, jogging around three to four months, and a full return to sports at six to nine months.
In rare cases where a large portion of the meniscus is lost and the patient is young, a meniscus transplant using donor tissue is an option. Recovery takes six to nine months, and most surgeons advise against returning to high-impact sports afterward.
Why Preserving the Meniscus Matters
The long-term health of your knee depends heavily on keeping as much meniscal tissue intact as possible. Removing even part of the meniscus shifts how forces travel through the joint, concentrating pressure on the bone surfaces and accelerating cartilage breakdown. Over a ten-year period, the total economic burden of meniscectomy actually exceeds that of repair ($31,528 vs. $22,590) because more meniscectomy patients eventually need knee replacements. This is why the trend in orthopedic surgery has shifted strongly toward repairing tears whenever the biology allows it.