A meniscus is a crescent-shaped piece of tough, rubbery cartilage that sits inside your knee joint, cushioning the space between your thighbone and shinbone. Each knee has two of them: a medial meniscus on the inner side and a lateral meniscus on the outer side. Together, they act as shock absorbers, stabilize the knee, and distribute your body weight evenly across the joint so that no single spot on the bone takes too much pressure.
What the Meniscus Is Made Of
The meniscus is about 70 to 75 percent water by weight. The rest is mostly collagen, the same structural protein found in tendons and skin, with about 90 percent of that collagen being the strong, rope-like type that resists tension. Small amounts of elastic proteins give it some flexibility, and specialized cells called fibrochondrocytes maintain the tissue over time.
This composition makes the meniscus uniquely suited to its job. It’s firm enough to bear heavy loads (your knee absorbs several times your body weight when you run or jump) but flexible enough to change shape slightly as the joint moves. Think of it as a living washer inside the knee that both cushions impact and keeps the bones tracking smoothly against each other.
Why Blood Supply Matters
One of the most important things about the meniscus is that most of it has no blood supply. Only the outer 25 percent, known as the “red zone,” receives blood flow. The inner 75 percent, the “white zone,” is essentially cut off from the body’s healing resources. This distinction has huge consequences if the meniscus gets injured, because tissue without blood flow has very limited ability to repair itself.
How Meniscus Tears Happen
Meniscus tears fall into two broad categories: traumatic and degenerative. In younger, active people, tears typically happen during a sudden twist or pivot with the foot planted, often during sports. These acute tears tend to be vertical or radial, meaning the cartilage splits along clean lines. The incidence of meniscus injuries in young, physically active populations can be as high as 8.27 per 1,000 person-years, roughly ten times the rate in the general population.
Degenerative tears are a different story. They develop gradually as the cartilage weakens with age and repeated use. Among people aged 50 to 90, about 31 percent have a meniscus tear, though many never know it. These tears tend to be horizontal or complex, and they often overlap with early osteoarthritis. Even among younger adults aged 18 to 39, around 5.6 percent have an asymptomatic tear that shows up on imaging but causes no problems.
Symptoms of a Torn Meniscus
A torn meniscus doesn’t always announce itself immediately. With small tears, pain and swelling may not show up until 24 hours or more after the injury. Common symptoms include:
- A popping sensation at the moment of injury
- Swelling and stiffness that builds over the first day or two
- Pain when twisting or rotating the knee
- Locking, where the knee feels stuck and won’t fully straighten
- Giving way, a sensation that the knee might buckle under you
Locking is a particularly telling sign. It happens when a flap of torn cartilage folds into the joint space and physically blocks motion. If you can’t straighten your knee all the way, that’s often what’s going on.
How a Meniscus Tear Is Diagnosed
Diagnosis usually starts with a hands-on exam. Your doctor will press along the joint line of the knee and perform specific bending and rotating maneuvers. The McMurray test, Apley test, and Thessaly test are the most common. A palpable click combined with pain during these tests strongly suggests a meniscus tear. However, physical exams alone aren’t perfectly accurate, so an MRI is typically ordered to confirm the diagnosis and reveal the tear’s exact location, size, and pattern.
Treatment: Repair vs. Removal
Not all meniscus tears need surgery. Some, especially small degenerative tears that cause only mild symptoms, can be managed with rest, physical therapy, and anti-inflammatory measures. When surgery is necessary, the two main options are meniscus repair and partial meniscectomy (trimming away the damaged portion).
The choice between them comes down largely to where the tear is. Tears in the outer red zone, which has blood supply, have a realistic chance of healing if stitched back together, so repair is preferred. Tears in the inner white zone won’t heal reliably even with stitches, so surgeons typically trim away the damaged tissue instead. Age matters too: younger patients are more likely to be candidates for repair, partly because preserving as much meniscus as possible helps protect the joint from arthritis later in life.
The trend in orthopedic medicine has shifted toward preserving the meniscus whenever possible. Removing cartilage solves the immediate problem but increases stress on the joint surface over time, raising the risk of osteoarthritis down the road.
Recovery After Meniscus Surgery
Recovery timelines differ significantly depending on the procedure. A partial meniscectomy (trimming) is the quicker recovery. Many people return to normal activities within a few weeks.
A meniscus repair is a longer process because the stitched tissue needs time to heal. Based on rehabilitation protocols from Massachusetts General Brigham, the typical timeline looks like this:
- Weeks 0 to 3: Partial weight-bearing with crutches and a brace
- Weeks 3 to 6: Continued partial weight-bearing, beginning gentle range-of-motion exercises
- Weeks 6 to 9: Transitioning off crutches and the brace once muscle control and a normal walking pattern return
- Months 3 to 5: Starting sport-specific training
- 6 months and beyond: Full return to sport, provided strength and functional testing meet specific benchmarks
Before clearing someone for unrestricted activity, doctors and physical therapists look for quad and hamstring strength within 90 percent of the uninjured leg, successful completion of a running program without pain or swelling, and hop tests that match the other side. These objective criteria help ensure the repair is solid and the knee is ready for the demands of sport or heavy physical activity.
Long-Term Outlook
A healthy meniscus is something most people never think about until it’s injured. But losing meniscus tissue, whether through a tear or surgical trimming, changes the mechanics of the knee. The remaining cartilage and bone surfaces take on more stress, which over years can accelerate wear and contribute to osteoarthritis. This is why orthopedic specialists increasingly prioritize repair over removal and why rehabilitation after surgery focuses so heavily on rebuilding the surrounding muscle strength that helps protect the joint.
For degenerative tears, maintaining a healthy weight, staying active with low-impact exercise, and building strong leg muscles are the most effective ways to keep symptoms manageable and slow further joint breakdown.