Vascular Supply

For Medical Students

Structure and Location

Blood reaches the meniscus from outside. A ring of vessels, the perimeniscal capillary plexus, lies in the capsular and synovial tissue around the peripheral border, and branches from it run inwards.

They do not get far. Conventional teaching gives the penetration as the peripheral 10 to 30 per cent of the width in an adult, more in a child and less with age.

That produces three zones, named by what a surgeon sees when the tissue is cut. The red zone peripherally, which bleeds. The white zone centrally, which does not. The red white zone between them, which is the judgement call.

Relations

The plexus is fed by the medial genicular arteries for this meniscus, reaching it through the capsule and the coronary ligament.

The horns are better supplied than the body, because vessels reach them through the bony attachment as well as from the periphery.

The inner part of the meniscus lies in synovial fluid and depends on it entirely.

Function

A tissue with a blood supply can mount a healing response. A tissue without one cannot, whatever is done to it.

That is the whole clinical content of this page. The zones are not a description of colour; they are a prediction about whether a repair will work.

Clinical Relevance

A tear in the red zone is repairable. A tear in the white zone is not, and resecting it is the alternative.

A tear in the red white zone may be repaired, and the decision depends on the patient, the tear pattern and what the tissue looks like.

In a child the vascular zone is wider, so tears that would not be repairable in an adult are repairable. Section 10 owns the paediatric decision.

MRCS Level

Structure and Location

The perimeniscal plexus is a circumferential network in the capsular and synovial tissue immediately peripheral to the meniscus. It is fed on the medial side by the superior medial and inferior medial genicular arteries, with a contribution from the middle genicular artery posteriorly.

Radial branches penetrate the peripheral tissue. Their depth is conventionally quoted as the outer 10 to 30 per cent of the width, and the figure falls through adult life.

The synovial fringe extends a short distance over both surfaces at the periphery and contributes to the supply of the outermost tissue.

At each horn the attachment carries its own vessels from the intercondylar area, so the horn tissue is vascular even where the adjacent body is not.

Relations

The plexus lies in the tissue a repair suture passes through, which is why peripheral repair techniques are described in terms of the capsular tissue as much as the meniscus.

The synovium at the periphery is the source of the cells and the vessels that cross into a healing tear, which is the rationale behind synovial abrasion and trephination.

The avascular inner tissue is in continuity with the synovial fluid, and its nutrition depends on fluid movement with joint motion rather than on diffusion through still fluid.

Blood Supply and Innervation

The supply and the innervation share a route. Nerve fibres run with the perimeniscal vessels and penetrate to a comparable depth, and mechanoreceptors are concentrated at the horns.

This gives a clinically useful parallel: tissue that can heal is tissue that can hurt. A peripheral tear is painful and repairable; a central degenerative lesion may be neither.

The horns are the exception in both respects, being vascular, innervated and the site of most of the proprioceptive endings.

Function

Healing of a meniscal tear needs vessels, cells and mechanical stability. Vascularity supplies the first two and the repair construct supplies the third.

Where vascularity is absent, adding stability alone does not produce healing, which is the reason white zone repair fails rather than simply being unproven.

The vascular gradient also explains the age effect. The same tear in the same place is less likely to heal in a sixty year old than in a twenty year old, and the difference is anatomical.

Clinical Relevance

Assess the zone at arthroscopy, not on imaging. The distance from the peripheral border is what matters, and it is measured where the tear is.

Trephination, synovial abrasion and fibrin augmentation all aim at the biology on this page. The techniques belong to 7.8 onwards.

In a vertical longitudinal tear within the red zone in a young patient, the anatomy favours repair strongly, and that case needs the least argument.

Age narrows the vascular zone, so a repair decision in an older patient is a different decision with the same tear.

The penetration figure on this page is standard teaching, registered and unchecked, and it is quoted as a range precisely because it varies.

FRCS Level

Relations

The relation that matters operatively is between the tear and the peripheral border, not between the tear and any anatomical landmark. Repairability is a distance.

In a knee with previous peripheral surgery or capsular scarring, the plexus may be disrupted and the zone narrower than its position suggests, which is an argument for judging the tissue rather than the geometry.

Function

The vascular argument sets a ceiling on what repair can achieve and an alternative explanation for failure. A repair that fails in the red zone failed mechanically; one that fails in the white zone failed biologically.

Distinguishing those two in a particular case changes what is done next, and it is an anatomical distinction made at the time of the first operation.

Clinical Relevance

Document the zone and the distance from the periphery in the operation note. It is the single most useful piece of information for whoever revises the knee.

Where the zone is marginal, the decision is shaped by what resection would cost in that particular knee rather than by the tear alone: a young patient with an intact cruciate and good cartilage loses more from resection than an older one.

Biological augmentation strategies target this page. Their mechanism is vascular and cellular, and their ceiling is the same anatomy.

In the meniscus of a child, the wider vascular zone changes the arithmetic in favour of repair for almost every tear, and Section 10 owns it.