A meniscus is a crescent-shaped wedge of tough, rubbery cartilage that sits inside your knee joint, acting as a cushion between your thighbone and shinbone. You have two in each knee: one on the inner side (the medial meniscus) and one on the outer side (the lateral meniscus). Together, they distribute your body weight across the knee, reduce friction, and help stabilize the joint during movement. Meniscus tears are one of the most common knee injuries, affecting roughly 60 to 70 out of every 100,000 people each year.
What the Meniscus Is Made Of
The meniscus is made of fibrocartilage, a tissue that’s tougher and more flexible than the smooth cartilage coating the ends of your bones. About 72% of the meniscus is water. Of the remaining solid material, around 90% is type I collagen, the same structural protein found in tendons and ligaments. This collagen-heavy composition gives the meniscus its unique ability to absorb compressive forces while still being slightly flexible.
The cells inside the meniscus vary depending on depth. Near the surface, they resemble the cells found in ligaments and tendons. Deeper inside, they look more like the cells found in joint cartilage. This gradient reflects the meniscus’s dual role: it needs to handle both tension and compression at the same time.
What the Meniscus Does
The meniscus performs several jobs at once. Its primary role is load distribution. When you walk, run, or jump, the forces traveling through your knee aren’t applied to a single point. Instead, the menisci spread that load across a wider area of the shinbone, protecting the joint cartilage underneath from concentrated stress. Without functioning menisci, the cartilage on the ends of your bones wears down much faster, which is why meniscus loss is strongly linked to arthritis later in life.
Beyond load distribution, the menisci help lubricate the joint by spreading synovial fluid (the slippery liquid inside the joint capsule) across the cartilage surfaces during movement. They also contribute to joint stability, helping prevent the thighbone from sliding too far forward or backward on the shinbone. And they play a role in proprioception, your knee’s ability to sense its own position, which matters for balance and coordination.
Medial vs. Lateral Meniscus
The two menisci in each knee aren’t identical. The medial meniscus (inner side) is generally described as C-shaped, while the lateral meniscus (outer side) is more O-shaped and circular. Despite having nearly the same volume, they differ in important ways. The lateral meniscus covers about 59% of its side of the shinbone, while the medial meniscus covers only about 50% of its side. The medial meniscus is slightly thicker on average but narrower overall.
The lateral meniscus is also more mobile. The medial meniscus is more firmly attached to the joint capsule and the medial collateral ligament, which anchors it in place but also makes it more vulnerable to injury during twisting movements. The lateral meniscus, being less tethered, can shift slightly during motion, which gives it some natural protection from tearing.
Blood Supply and Healing Zones
One of the most important things about the meniscus is how its blood supply is distributed, because blood supply directly determines whether a tear can heal on its own. The meniscus is divided into three zones based on vascularity:
- Red-red zone: The outer edge of the meniscus, closest to the joint capsule, has a good blood supply. Tears here have the best chance of healing.
- Red-white zone: The middle section has partial blood flow. Tears in this area sometimes heal, sometimes don’t.
- White-white zone: The inner edge has essentially no blood supply. Tears here rarely heal on their own, which is why inner meniscus tears often require surgical trimming rather than repair.
This is why two people with meniscus tears can get very different treatment plans. The location of the tear matters as much as the size.
How Meniscus Tears Happen
Meniscus tears fall into two broad categories: traumatic and degenerative. Traumatic tears typically happen during sports or physical activity when the knee twists while bearing weight, such as planting your foot and pivoting, or landing awkwardly from a jump. These are more common in younger, active people. The incidence among high school athletes is about 5.1 per 100,000.
Degenerative tears happen gradually as the meniscus weakens with age. In older adults, the fibrocartilage becomes less resilient, and a tear can develop from something as minor as squatting or stepping off a curb. These tears are common and don’t always cause symptoms. Many people have degenerative meniscus tears visible on MRI without ever experiencing knee pain.
Common symptoms of a symptomatic tear include pain along the joint line, swelling that develops over several hours, a catching or locking sensation when bending the knee, and difficulty fully straightening the leg. Some people describe a “giving way” feeling during walking or turning.
How Tears Are Diagnosed
A doctor can often identify a meniscus tear during a physical exam by moving your knee and leg into specific positions, watching you walk, and asking you to squat. These maneuvers stress the meniscus and reproduce the catching or pain associated with a tear. MRI is the standard imaging tool for confirming the diagnosis, revealing the tear’s location, size, and pattern, all of which guide treatment decisions.
Treatment and Recovery Timelines
Not every meniscus tear needs surgery. Small tears in the outer (red-red) zone, and many degenerative tears, can be managed with rest, ice, anti-inflammatory medications, and physical therapy focused on strengthening the muscles around the knee. If pain and mechanical symptoms like locking persist after several weeks of conservative treatment, surgery becomes more likely.
When surgery is needed, there are two main approaches. Meniscus repair stitches the torn pieces back together and is preferred when the tear is in the blood-rich outer zone, because the tissue has a realistic chance of healing. Partial meniscectomy trims away the damaged portion and is used when the tear is in the inner zone where healing won’t occur. Repair preserves more of the meniscus and protects against future arthritis, but it requires a longer recovery.
After a meniscus repair, the first three weeks focus on protecting the repair site. You’ll use crutches, wear a brace locked in a straight position, and limit knee bending to less than 90 degrees. From weeks three to six, you continue partial weight bearing while gradually working on range of motion. Around six weeks, most people can ditch the crutches and brace once they’ve regained adequate muscle control and a normal walking pattern.
Weeks nine through twelve are a transitional period where strengthening exercises ramp up. Between three and five months, sport-specific training can begin if muscle strength in the repaired leg reaches at least 90% of the other leg. Full, unrestricted return to sport typically happens at six months or later, once strength and hop tests show symmetrical performance between legs.
Recovery after a partial meniscectomy is significantly faster. Most people are walking without crutches within one to two weeks and can return to normal activities in four to six weeks, since there’s no repaired tissue that needs time to heal.