The knee meniscus is a pair of C-shaped cartilage pads that sit between the thigh bone and the shin bone, acting as shock absorbers, stabilizers, and load distributors for one of the most used joints in the body. This article breaks down the anatomy of the knee meniscus, including its structure, blood supply, function, and the types of tears that commonly affect it. Understanding this small but vital structure helps you make sense of knee pain, imaging reports, and treatment options.
The meniscus is a fibrocartilage structure shaped like a crescent or a wedge. Each knee has two of them: the medial meniscus on the inner side and the lateral meniscus on the outer side.
Unlike bone, cartilage does not show up clearly on a standard X-ray. This is why meniscus injuries are usually confirmed with an MRI.
The meniscus is not a simple flat disc. It is thicker at the outer edge and thinner toward the center, which helps it conform to the rounded surfaces of the knee joint.
The knee is made up of the femur (thigh bone), the tibia (shin bone), and the patella (kneecap). The menisci rest on the flat top surface of the tibia, called the tibial plateau.
They sit between the femoral condyles above and the tibial plateau below, forming a cushion that fills the gap between two curved surfaces.
The meniscus is built mostly of water, collagen, and specialized cells. Its strength comes from the way collagen fibers are arranged.
Most of the collagen is type I, which gives the tissue its tensile strength. This is the same type of collagen found in tendons.
The meniscus is roughly 70 percent water, and that water content is a big part of what allows it to absorb load without collapsing.
Only the outer portion of the meniscus receives a direct blood supply. This single fact shapes almost everything about how meniscus injuries heal.
Surgeons often describe the meniscus in three zones based on blood flow.
This is why a small tear near the outer edge may heal on its own, while a tear in the inner zone often needs surgical trimming or repair.
The meniscus performs several jobs at once. It is part shock absorber, part stabilizer, and part lubricator.
When you walk, run, or jump, forces travel through the knee that can be several times your body weight. The meniscus helps spread that load across a wider area.
Remove a meniscus entirely and the contact pressure on the knee cartilage can rise sharply, which is one reason surgeons try to preserve as much tissue as possible.
Doctors classify meniscus tears by their shape, location, and how they relate to the blood supply. This description guides treatment.
| Feature | Medial Meniscus | Lateral Meniscus |
|---|---|---|
| Shape | C-shaped, open curve | More circular |
| Size | Larger | Slightly smaller |
| Attachment | Firmly attached to joint capsule and MCL | Looser attachment, more mobile |
| Tear frequency | More common | Less common |
| Mobility | Relatively fixed | Relatively mobile |
| Typical injury | Twisting with a planted foot | Deep squatting or twisting |
Meniscus tears can result from a single traumatic event or from gradual wear over time. The mechanism often differs between younger and older people.
Meniscus problems do not always cause dramatic pain. Some people feel a dull ache that comes and goes.
Others experience a sharp catch or a locking sensation that makes the knee feel stuck.
A physical exam often starts with specific tests that rotate and compress the knee. These tests help localize the pain to the meniscus.
Imaging then confirms the diagnosis and shows the tear pattern. MRI remains the most useful tool for soft tissue detail.
Not every meniscus tear needs surgery. Many degenerative tears respond well to conservative care.
Treatment depends on the tear type, location, age, activity level, and whether the knee is locked.
The meniscus protects the articular cartilage from excessive load. When too much meniscus is removed, the risk of early knee osteoarthritis rises.
Modern orthopedic practice favors repair whenever the tear pattern and blood supply allow it.
The knee meniscus is a small structure with a large role. Its wedge shape, layered collagen, and limited blood supply explain both how it works and why it is prone to injury.
Knowing the anatomy of the knee meniscus helps you understand your own knee pain, read an MRI report with more confidence, and have a clearer conversation with your doctor about treatment. Whether the issue is a sudden twist or years of wear, the meniscus sits at the center of knee health.
The meniscus is made mostly of water and type I collagen, along with proteoglycans and specialized cells called fibrochondrocytes. The collagen fibers are arranged in circumferential, radial, and oblique patterns that give the tissue strength and resilience.
Each knee has two menisci: the medial meniscus on the inner side and the lateral meniscus on the outer side. They sit on the tibial plateau between the femur and the tibia.
The medial meniscus is injured more often. It is larger and more firmly attached to the joint capsule and the medial collateral ligament, which limits its movement and makes it more vulnerable to twisting forces.
Only the outer third of the meniscus receives a direct blood supply. The inner two-thirds rely on synovial fluid for nutrition, which is much slower and less effective for healing. Tears in the inner zone often do not repair on their own.
Some tears can heal or become pain-free without surgery, especially small tears in the outer vascular zone and many degenerative tears. Conservative treatment with physical therapy and activity modification is often tried first.
During walking, the meniscus spreads load across the knee joint, absorbs impact, and helps stabilize the femur on the tibia. It also helps distribute synovial fluid to lubricate the cartilage.
A bucket-handle tear is a type of longitudinal meniscus tear where a portion of the meniscus displaces into the joint. It often causes locking, a block to full knee extension, and significant pain.
Diagnosis usually starts with a physical exam, including joint line tenderness and tests like the McMurray or Thessaly test. MRI is commonly used to confirm the tear and show its pattern and location.
Removing part of the meniscus can increase contact pressure on the articular cartilage, which raises the long-term risk of osteoarthritis. This is why surgeons aim to preserve as much meniscus tissue as possible.
The red-red zone is the outer third of the meniscus, where blood vessels are present. Because of this blood supply, tears in this zone have the best chance of healing, whether treated conservatively or with surgical repair.
