Why does the meniscus matter for knee function?

Written by Dr Sean Leo, a consultant orthopaedic surgeon whose clinical focus is the knee, sports injuries and the lower limb.

Last updated: 9 October 2026.

The main function of the meniscus is to transmit load across the knee joint. Each knee has two menisci: C-shaped pads of cartilage that sit between the thigh bone (femur) and the shin bone (tibia), one on the inner side and one on the outer side. They also help absorb shock and steady the knee.

What does the meniscus do in the knee?

Each knee has two menisci: C-shaped pads of cartilage that sit between the thigh bone (femur) and the shin bone (tibia), one on the inner side and one on the outer side. Their main job is to carry and spread the load that passes through the joint. They also help absorb shock and steady the knee.

• The main function of the meniscus is to transmit load across the knee joint.
• Secondary roles include shock absorption, joint stability, lubrication, nutrition and the sense of where the joint is in space (proprioception).
• The medial meniscus is on the inner side of the knee and the lateral meniscus is on the outer side.

More on how the meniscus handles weight

When weight comes down through the knee, the C-shaped meniscus is squeezed. Axial forces compress the menisci and produce “hoop” (circumferential) stresses. The collagen fibres that run around the length of the C-shape turn that downward force into tension along the fibres.

The meniscus is made of a dense matrix that is mostly water (about 72%) and collagen (about 22%), with cells in between. These proportions vary with age, injury and joint condition.

What does this page cover?

• What does the meniscus do in the knee?
• How much of the knee’s load goes through the meniscus?
• Why are some parts of the meniscus better supplied with blood than others?
• How do meniscus tears happen?
• How do repair and meniscectomy compare in the long term?
• When should a knee problem be checked urgently?
• Where can you read more, and what is worth discussing at an assessment?

How much of the knee’s load goes through the meniscus?

In studies of the extended knee, roughly 40–60% of the load passing through the joint is carried through the meniscus, and more in a bent knee.

• The figure comes from biomechanical studies, so it describes the knee in general terms rather than any one person’s knee.
• The share carried by the meniscus rises as the knee bends.

Why are some parts of the meniscus better supplied with blood than others?

Only the outer rim of the meniscus has a meaningful blood supply. This is roughly the outer 10–30% of the medial (inner-side) meniscus and the outer 10–25% of the lateral (outer-side) meniscus. Because of that limited blood supply, only certain types of tear are feasible to repair (Fox et al., 2015).

More on “red” and “white” zones

You may see the outer, blood-supplied rim called the red zone and the inner part the white zone. These labels are a rough guide only. A 2019 European consensus (the European Society of Sports Traumatology, Knee Surgery and Arthroscopy, ESSKA) advises against relying on them, because blood supply changes through life and is often not directly assessable during surgery.

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How do meniscus tears happen?

Traumatic tears generally occur in younger, active people. Degenerative tears may reflect cumulative stress.

• A traumatic tear follows an injury.
• A degenerative tear may reflect cumulative stress.

Symptoms, assessment and treatment are covered in the meniscus repair surgery guide.

How do repair and meniscectomy compare in the long term?

In traumatic tears, long-term outcomes were reported to be worse after partial meniscectomy (surgical removal of the torn part of the meniscus) than after repair. This is an association, not proof that one causes the other.

• In some studies of traumatic tears, repair was followed by less osteoarthritis (wear-related arthritis of the joint) than meniscectomy.
• This is one reason surgeons consider preserving the meniscus where that is possible.
• Repair does not always heal. In one consensus review, early repeat arthroscopy (a second keyhole procedure) was needed in 16.5% of repairs versus 1.4% of meniscectomies in the short term (ESSKA 2019).

More on how strong this evidence is

The studies behind the comparison of repair and meniscectomy describe groups of people, so they do not predict what will happen in any one knee.

When should a knee problem be checked urgently?

Where can you read more, and what is worth discussing at an assessment?

A knee problem involving the meniscus is usually thought through in three parts: the structure (what the tear is and where it sits), the patient (age, activity and general health) and the goal (what you want to be able to do). An assessment brings together what happened, an examination and any imaging that helps, so that you and your clinician can decide what to do next. An appointment supports an informed decision. It is not a commitment to surgery.

• Read how a meniscus tear is assessed and treated on the meniscus repair surgery page.
• Browse the Knee Hub for other knee problems.
• Read about the symptoms of a torn meniscus.
• Read about what knee popping and cracking can mean.
• Read about meniscus injury in athletes.

References

1. Fox AJS, Wanivenhaus F, Burge AJ, Warren RF, Rodeo SA. The human meniscus: a review of anatomy, function, injury, and advances in treatment. Clin Anat. 2015;28(2):269–287. doi:10.1002/ca.22456. PMID:25125315.
2. Kopf S, Beaufils P, Hirschmann MT, et al. Management of traumatic meniscus tears: the 2019 ESSKA meniscus consensus. Knee Surg Sports Traumatol Arthrosc. 2020;28(4):1177–1194. doi:10.1007/s00167-020-05847-3. PMID:32052121. PMCID:PMC7148286.