Tibial Spine

For Medical Students

Structure and Location

The tibial spine, or intercondylar eminence, is the ridge of bone between the two plateaux. It has a medial and a lateral tubercle, and it divides the intercondylar area into an anterior and a posterior part.

It is not an articular surface. It sits below the level of the plateaux and between them, in the space occupied by the cruciates.

Relations

In front of and around the spine, in the anterior intercondylar area: the anterior cruciate attachment, the anterior root of the medial meniscus most anteriorly, and the anterior root of the lateral meniscus close to the cruciate attachment.

Behind the spine, in the posterior intercondylar area: the posterior roots of both menisci, and then the posterior cruciate, which attaches lowest, on the posterior surface of the bone below the plateau.

The transverse intermeniscal ligament runs across the front, joining the two anterior horns.

Function

The spine is where the structures that control anteroposterior translation and hold the menisci in place are anchored. It bears tension rather than compression.

Because the two tubercles rise on either side, they also provide a small amount of bony resistance to side to side translation of the femur.

Clinical Relevance

Everything attached here is attached in a small area, so a single bony injury can detach several structures at once.

In children the anterior cruciate commonly fails by avulsing its tibial attachment rather than tearing, because the bone is weaker than the ligament. Management belongs to Section 10.

MRCS Level

Structure and Location

Name the attachments in order from front to back. The anterior root of the medial meniscus. The anterior cruciate ligament, on the anterior intercondylar area lateral to and behind that root. The anterior root of the lateral meniscus, which overlaps the cruciate attachment. The spine itself with its two tubercles. The posterior root of the lateral meniscus. The posterior root of the medial meniscus. The posterior cruciate, descending onto the posterior surface.

The tibial footprint of the anterior cruciate is conventionally described as of the order of 17 mm front to back and 11 mm across, which is broader than its femoral attachment.

The overlap between the anterior cruciate attachment and the anterior root of the lateral meniscus is the point that matters, because it means a tunnel placed on the cruciate footprint can involve the root.

Relations

The anterior cruciate attachment lies in front of and lateral to the medial tubercle, with the fibres fanning out onto the intercondylar area.

The posterior cruciate attachment is not on the spine but behind and below it, in a depression on the posterior surface of the tibia, conventionally described as about 1 cm below the joint line. That is why it is approached from behind rather than from within the notch.

The popliteal artery lies immediately behind the posterior cruciate attachment, separated from it by capsule only. That is the single most important relation in this chapter.

The transverse intermeniscal ligament and the anterior horns lie across the anterior area and are the structures encountered when the notch is cleared from the front.

Blood Supply and Innervation

Supply to the spine and the intercondylar area comes from the middle genicular artery posteriorly and from the inferior genicular arteries through the capsular attachments.

The middle genicular is the vessel shared with both cruciates, so the attachment and the ligament have the same supply.

Innervation is from articular branches of the tibial nerve, and the cruciate attachments carry mechanoreceptors. 2.7.5 and 2.7.10 own the detail for the anterior cruciate.

Function

The spine anchors the restraints to anteroposterior translation at their tibial end. Its position between the plateaux means the ligaments pull on bone that is braced on both sides.

The meniscal roots anchored here resist the meniscus being extruded peripherally under load. A root that has detached allows the meniscus to move, and the meniscus then stops functioning even though it is intact.

Clinical Relevance

The posterior cruciate attachment's relationship to the popliteal artery is the reason tibial inlay and transtibial techniques are discussed as different risks rather than different preferences. Section 7 owns the comparison.

Tibial spine avulsion in a child is an anterior cruciate injury with the ligament intact. Recognising it as such changes the treatment. 6.101 and 10.35 own it.

Meniscal root attachments here are close enough to cruciate tunnels that root injury during reconstruction is a recognised hazard rather than a theoretical one.

Clearing the notch from the front, as is done to improve visualisation, can divide the transverse intermeniscal ligament and the anterior root of the lateral meniscus if the landmarks are not respected.

FRCS Level

Relations

In the posterior intercondylar area the operative margin is capsule. There is no muscular or fatty layer between the posterior cruciate attachment and the popliteal artery, and flexing the knee does not reliably create one.

Anteriorly the margin is the root attachments, which are soft tissue structures sharing the footprint with the cruciate.

Function

This small area carries the tibial anchorage of every structure controlling translation and of every structure keeping the menisci in place. Any procedure here competes for the same bone.

That competition is the practical constraint in combined injuries: a cruciate tunnel, a root repair and an osteotomy can all want the same cubic centimetre.

Clinical Relevance

In combined cruciate and root injury, the sequence of fixation is determined by which structure's anchorage would be compromised by the other, and that is an anatomical judgement made before the skin is opened.

In revision cruciate reconstruction, previous tibial tunnels have usually removed part of the spine, and what remains determines whether a new tunnel can be placed or has to be grafted first.

In posterior cruciate surgery the artery is the limiting structure, and every published technique is a different answer to the same anatomical problem.

Published descriptions of these footprints are all quantitative. None of those dimensions appears here, because none could be verified. Decision 005 records that, and this is the page on which it costs the reader most.