Root Attachments

For Medical Students

Structure and Location

A root is the bony attachment of a meniscal horn. The medial meniscus has two: an anterior root and a posterior root.

The anterior root attaches in the anterior intercondylar area, in front of the tibial attachment of the anterior cruciate ligament.

The posterior root attaches in the posterior intercondylar area, just in front of and medial to the tibial attachment of the posterior cruciate ligament.

Both are short, broad and fibrous, and both insert into bone through a transitional zone rather than simply resting on it.

Relations

The anterior root lies close to the anterior cruciate's tibial footprint and to the transverse intermeniscal ligament.

The posterior root lies close to the posterior cruciate's tibial attachment and to the posterior root of the lateral meniscus.

Both sit in the intercondylar area rather than on the articular surface, so neither is under the femoral condyle.

The tibial spine lies between them.

Function

A root anchors the circumferential collagen of the meniscus. The hoop tension generated when the wedge is loaded is transmitted into bone through the roots.

Lose a root and the hoop cannot be tensioned. The meniscus then moves outwards under load instead of resisting, which is extrusion, and it stops transmitting load.

That is why a root is not simply the end of the meniscus. It is the part through which the whole mechanism works.

Clinical Relevance

A posterior root tear produces meniscal extrusion and behaves mechanically like a total meniscectomy, even though almost all the tissue is present.

Root tears are therefore repaired rather than debrided where the tissue allows, and the aim is to restore the attachment rather than to tidy the tear.

The pathology belongs to 6.34 and the repair to 7.14. What belongs here is why it matters.

MRCS Level

Structure and Location

Describe each root by its landmarks rather than by a coordinate. The posterior root of the medial meniscus attaches in the posterior intercondylar area, anterior to the posterior cruciate attachment and medial to the posterior root of the lateral meniscus, with the medial tibial articular margin immediately lateral to it.

The anterior root attaches in the anterior intercondylar area, anterior and medial to the anterior cruciate tibial footprint, and the two footprints can overlap. That overlap is the anatomy behind iatrogenic anterior root injury during cruciate tunnel drilling.

Each root is an enthesis with the four zone structure of a direct tendon insertion, so its failure mode is avulsion at the bone rather than tearing in the substance.

Accessory fibres run from the posterior root region to the tibia and occasionally to the posterior cruciate, and their presence is variable.

Relations

Posterior root: posterior cruciate attachment behind, lateral meniscal posterior root laterally, medial articular margin laterally and slightly anteriorly, and the posterior capsule behind all of it with the popliteal vessels beyond.

Anterior root: anterior cruciate footprint behind and laterally, transverse intermeniscal ligament continuing laterally, and the fat pad in front.

The roots are the only parts of the meniscus with a direct bony blood supply, which makes them better vascularised than the adjacent body.

Both lie in a region crowded with other attachments, which is covered on 2.2.3.

Blood Supply and Innervation

Root tissue receives vessels from the intercondylar area through the bony attachment and from the perimeniscal plexus peripherally. It is therefore among the better supplied meniscal tissue.

That vascularity is the reason root repair heals at all, and it is one of the arguments for repairing rather than resecting.

Mechanoreceptors are concentrated in the horns and roots, so a root carries proprioceptive as well as mechanical function. 2.7.10 covers the equivalent for the cruciate.

Function

The root converts the meniscus from a loose wedge into a tensioned ring. The whole load sharing mechanism on 2.5.4 depends on both roots being attached.

Partial root detachment reduces hoop tension in proportion to the fibres lost, so root pathology is graded rather than binary, and partial lesions matter.

Because the posterior root resists the posterior horn being pushed outwards and backwards, its loss also reduces the horn's contribution to anteroposterior stability.

Clinical Relevance

Recognise posterior root tear as a distinct entity rather than as a posterior horn tear. The imaging sign is extrusion with a vertical gap at the root on coronal images, and 5.6 owns the criteria.

The anterior root's overlap with the anterior cruciate footprint means cruciate reconstruction can injure it, and that is a recognised iatrogenic lesion rather than a theoretical risk.

Repair aims to restore the footprint, so fixation is placed at the anatomical attachment and not simply nearby. 7.14 owns the technique.

In the varus knee, root failure and progressive extrusion accelerate medial compartment loading, which links root pathology to alignment.

FRCS Level

Relations

The crowding of the posterior intercondylar area is the operative problem. The medial root, the lateral root and the posterior cruciate attachment are within a small space, and fixation for one can compromise another.

Behind all of them is capsule and then the popliteal artery, which is the constraint on any transtibial tunnel directed posteriorly.

Function

Root repair restores a mechanism, which is a different claim from restoring tissue continuity. The test of success is whether extrusion resolves and the hoop tensions, not whether the tissue has stuck together.

That distinction explains why anatomical footprint restoration matters: a root fixed medial or anterior to its footprint shortens the meniscus and tensions the hoop in the wrong direction.

Clinical Relevance

In a posterior root tear with a correctable varus deformity, address both. Repairing a root in a limb that will keep overloading it is a predictable failure, and the reasoning is anatomical.

In combined cruciate and root pathology, plan tunnel position with the root footprints in mind, because the space is shared.

In revision, a previously fixed root may have healed in a non anatomical position, and the extrusion on imaging will say so.

All published root footprint descriptions are quantitative, given as distances from the cruciate attachments and the articular margins. None appears here, and that absence is most costly on this page and on 2.2.3. Decision 006 records why, and the figure register is where a reviewer should add them.

Fellowship Level

Clinical Relevance

Four decisions that turn on root anatomy.

Repair or resect a posterior root tear. The anatomical argument for repair is that the tissue is vascular and the mechanism is recoverable. The argument against, in a particular knee, is cartilage already lost: restoring the hoop helps a joint that still has a surface to protect.

Simultaneous osteotomy. In the varus knee with a root tear, the root and the alignment are one problem. Section 7 owns the combination; the anatomy says they cannot be separated.

Tunnel planning in combined injury. The posterior intercondylar area holds both roots and the posterior cruciate. Where all three need addressing, the order and the trajectories are planned together, and the posterior capsule and artery set the limit.

The iatrogenic anterior root. Cruciate tunnel placement that respects the cruciate footprint can still take part of the anterior root, because the footprints overlap. Recognising it at the time allows repair; finding it later usually does not.

The anatomy on this page does not change between these four. What changes is how much of the mechanism is left to protect.