Meniscus tear: a knee specialist's guide— full professional article

What is the meniscus and what does it do?

The meniscus is a fibrocartilaginous structure that sits around the periphery of the knee joint. Every knee has two menisci.

The medial meniscus lies on the inner side of the knee.

The lateral meniscus lies on the outer side.

Meniscal tissue is rubbery and elastic, shaped almost like a complete ring.

The meniscus performs several important jobs in the knee, including distributing load across the joint, helping nourish the articular cartilage, and absorbing shock during movement.

In short, the menisci are essential for the normal structure and function of the knee, and for protecting its cartilage.

Anatomically, each meniscus is usually described in three parts: an anterior horn, a body, and a posterior horn.

What is a meniscus tear, and what types are there?

A meniscus tear is exactly what it sounds like: a tear within the meniscal tissue. A tear can involve any part of the meniscus, in any plane or pattern.

Broadly, meniscus tears are classified as either traumatic tears or degenerative tears.

A traumatic tear happens in an otherwise healthy, structurally normal knee following an injury.

A degenerative tear happens in a knee that already shows wear and tear, meaning cartilage or meniscal tissue that has begun to break down, even when cartilage loss is not yet advanced. Younger, active patients tend to have traumatic tears, while older adults more often have degenerative tears.

How does a meniscus tear happen?

A traumatic tear usually follows an injury, most often a forceful twisting movement of the knee. Football and similar pivoting sports are classic examples.

A degenerative tear can also follow a twist, but far less force is needed to tear meniscal tissue that is already worn.

In many cases there is no clear injury at all, and patients simply notice knee pain that seemed to appear for no obvious reason.

Why does a torn meniscus hurt?

The knee is rich in pain receptors, and unstable or partially detached tissue can generate pain. Think of a partly torn fingernail, or a flap of skin still attached along one edge, that hurts every time it moves.

In the same way, a torn meniscus becomes mechanically unstable, so it tends to hurt whenever the knee is loaded or moved.

What is a bucket-handle meniscus tear?

A bucket-handle tear is a long, longitudinal traumatic tear that runs from the anterior horn through the body to the posterior horn, while the front and back roots usually stay attached. The torn segment flips into the middle of the joint, creating the appearance of a bucket handle.

Because that fragment tends to shift toward the center of the knee, it often causes mechanical locking, blocking the joint so the knee cannot fully straighten.

What does a locked knee mean?

A locked knee means the knee cannot be fully straightened, even passively, because something inside the joint is physically blocking the last few degrees of extension.

That blockage may be a loose body, a bucket-handle meniscal fragment, a torn ligament stump, foreign material, or another problem inside the joint.

What is a meniscal root tear?

The meniscus is anchored to the tibia (shin bone) at an anterior root and a posterior root. The posterior root attachment is the one most often injured in root tears.

A root tear is essentially an avulsion of the root off the bone. Once the anchor is lost, the meniscus is pushed out of the joint and can no longer do its job, so the knee behaves much like a knee with no meniscus at all, similar to having the whole meniscus removed.

Why does a meniscal root tear matter?

Because the knee now behaves as if the meniscus is missing, two main concerns stand out:

Accelerated degenerative wear of the articular cartilage.

A higher risk of insufficiency fractures around the knee.

What is an insufficiency fracture around the knee?

Without the meniscus to share the load, certain focal areas of the joint surface are exposed to more stress than they can withstand and may begin to collapse. This is not a classic traumatic fracture but a subchondral insufficiency, or compression, injury just beneath the cartilage.

An insufficiency fracture is often found together with a posterior root tear, which is frequently the underlying cause.

What is a discoid meniscus?

A normal meniscus is C-shaped, like a crescent moon.

A small number of people are born with a meniscus that is not crescent-shaped but closer to a complete disc, either a full or a partial disc shape.

Another variant considered discoid involves incomplete attachment of the meniscus to the joint capsule around its rim.

A discoid meniscus can affect either meniscus but is far more common on the lateral (outer) side.

On its own, a discoid meniscus often causes no symptoms at all.

It usually becomes a problem only when it tears, or when overly mobile meniscal tissue produces mechanical symptoms such as a clunking sensation on the outer side of the knee.

How is a meniscus tear diagnosed?

As with everything in medicine, assessment begins with a careful history: how the injury happened, where the pain is, any mechanical symptoms, what makes it better or worse, previous treatments, and the patient's functional goals.

The second step is a thorough physical examination of the knee.

Imaging comes next. MRI is the standard scan for a suspected meniscus tear.

How is a meniscus tear treated?

Treatment can be non-operative (without surgery) or operative (with surgery).

Non-operative care centers on structured physiotherapy.

The operative treatment is knee arthroscopy.

In this minimally invasive procedure, a small camera and fine instruments are introduced through tiny keyhole incisions at the front of the knee.

The surgeon then systematically inspects each compartment and the meniscal tissue on a high-definition monitor.

Once a tear is confirmed, how do surgeons treat it?

There are generally two ways to address a meniscus tear during knee arthroscopy.

Partial meniscectomy: removing the unstable, torn fragment that is driving the symptoms.

Meniscal repair (suture repair): stitching the tear back together, reserved for selected tear patterns and patients.

The decision to repair is made together with the patient. Factors that tend to favor repair include:

Younger age, since repair is favored more in younger patients.

A tear near the outer rim, in the more vascular red zone, where healing potential is better.

Good tissue quality, since healthier tissue is more likely to heal.

An acute tear, since fresher injuries generally heal better than older ones.

A concurrent ACL reconstruction, which can improve the healing environment and may make repair more appropriate.

The meniscus has a limited blood supply and is nourished largely by the joint fluid. Blood flow to the rim declines with age, which lowers the ability of a tear to heal.

Even when repair is chosen, healing is not guaranteed. Symptoms can return, and a repeat arthroscopy with partial meniscectomy may occasionally be needed.

Does every meniscus tear need arthroscopy?

No, absolutely not.

An MRI diagnosis on its own is never a reason to operate.

Surgery makes sense when symptoms clearly justify it and the patient's goals outweigh the risks of the procedure.

Mechanical locking from a bucket-handle tear is a common reason to operate, in order to restore full extension and a normal range of motion.

How is a meniscal root tear treated?

This is a special situation, because the knee behaves as if it has no meniscus. There is a strong case for anatomic root repair, reattaching the root back to the bone to restore load sharing, protect the cartilage, and reduce the risk of an insufficiency fracture.

Because the repair is made to bone, which has a richer blood supply, the healing potential is more favorable than for many tears in the middle of the meniscus.

For this reason, there is rarely a strict age limit for root repair, although advanced arthritis can make repair pointless.

In an end-stage arthritic knee, root repair may no longer be appropriate.

Does knee arthroscopy cause arthritis?

In general, the less healthy the meniscal tissue, the higher the long-term risk of degenerative change in the knee.

A torn meniscus is already mechanically compromised, so over time the knee may wear faster than a knee without a tear, whether or not surgery is performed.

What are the goals of meniscus surgery?

To improve quality of life and reduce pain, either by removing unstable tissue or by repairing the tear when the criteria are met.

To preserve the biology of the joint, whenever repair is feasible, in order to lower the future risk of cartilage wear.

In summary, partial meniscectomy targets the symptomatic, unstable fragment. Future cartilage risk is driven mainly by the underlying tear and its biology, not by the operation alone.

What is a discoid meniscus, in more detail?

A discoid meniscus looks more like a disc or a coin than a crescent. It lacks the usual anterior horn, body, and posterior horn pattern, and instead forms a thickened discoid plate.

It is a variant that people are born with, and it is far more common on the lateral (outer) side than on the medial side.

Most discoid menisci cause no symptoms.

When does a discoid meniscus cause symptoms?

It usually becomes symptomatic when it tears.

Some discoid menisci are overly mobile because they lack stable attachments around the rim. They shift back and forth inside the joint and produce a clunk that patients may feel or even hear.

How is a discoid meniscus treated?

A discoid meniscus that causes no symptoms needs no treatment.

A symptomatic tear is managed like any other meniscus tear that affects quality of life.

A symptomatic, overly mobile discoid meniscus is often treated with knee arthroscopy, reshaping it toward a more normal C-shape (saucerization), sometimes with stabilizing sutures to reattach the rim to the capsule.