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Anatomy · Joints & cartilage

Meniscus

'Little moon' in Greek

Lower limb · knee

The menisci are two C-shaped wedges of fibrocartilage lying between the femoral and tibial condyles of each knee. They deepen the shallow tibial surface, spread the load across the joint, absorb shock and help with stability. Only their outer rim has a blood supply, so tears in the inner zone heal poorly, and what a footballer calls a torn cartilage is usually a torn meniscus.

How to spot them

  • ▸Two crescents in each knee: the larger C-shaped medial and the more circular lateral
  • ▸Wedge-shaped in cross section: thick at the outer border, thin at the inner free edge
  • ▸The medial meniscus is fixed to the medial collateral ligament, the lateral is more mobile
  • ▸Anchored to the tibial plateau at their horns; joined at the front by the transverse ligament

What to know

Two crescent-shaped pads of fibrocartilage lie between the femur and tibia in each knee

Meniscus — the medial and lateral menisci.

Only the outer rim has a blood supply, so tears in the inner part rarely heal on their own

Meniscus — the red zone versus the white zone.

Its name is Greek for 'little moon' and describes its shape

Meniscus — from meniskos, a crescent.

Attached to the medial collateral ligament, one crescent is much more often injured than the other

Meniscus — the medial one (OpenStax says about twenty times as often).

A tear that flips into the middle of the joint like a handle, locking it

Meniscus — the bucket-handle tear.

Key ideas

  • Load-sharing: the menisci transmit a substantial part of the compressive load across the knee, and the joint suffers when they are removed.

Quick-fire facts

  • •OpenStax: the medial and lateral menisci are two articular discs between the femur and tibia; some areas lack an arterial supply and heal poorly.
  • •The medial meniscus is anchored to the tibial collateral ligament, making it less mobile and more prone to injury (OpenStax: about 20 times more likely to be injured than the lateral).
  • •The lateral meniscus is more circular and covers a larger proportion of the tibial surface.
  • •Blood supply comes from the geniculate arteries and reaches only the outer third (the 'red-red' zone).
  • •The meniscofemoral ligaments (of Humphry and Wrisberg) link the lateral meniscus to the femur.
  • •The word 'cartilage' in sports medicine often means meniscus: 'torn cartilage'.
  • •Total removal of the meniscus (meniscectomy) increases the risk of early osteoarthritis, so repair or partial removal is preferred where possible.

Drill it — 7 cards

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Sources