Tibial Plateau

For Medical Students

Structure and Location

The tibial plateau is the upper surface of the proximal tibia, and it is two surfaces rather than one.

The medial plateau is larger, oval, and concave in both planes. The lateral plateau is smaller, rounder, and convex in the sagittal plane while being slightly concave across. Between them lies the intercondylar area with the tibial spine.

Both surfaces are tilted so that the back of the plateau sits lower than the front. That posterior slope is a normal feature and its magnitude varies between people.

The lateral plateau also sits slightly higher than the medial in most knees.

Relations

The menisci sit on the plateau margins, thick peripherally and thin centrally, so each deepens its surface. The lateral meniscus does more of that work, because the surface underneath it is convex.

The cruciate and meniscal root attachments lie in the intercondylar area rather than on the articular surface itself.

The capsule attaches around the plateau margin, and the deep layer of the medial collateral attaches to both the meniscus and the bone just below the margin.

Function

The plateau receives load across an area much smaller than the femoral surface that delivers it, and the menisci exist to increase that area.

A concave medial surface constrains the femoral condyle. A convex lateral surface does not, so the lateral side depends on the meniscus and the soft tissues for its stability.

Posterior slope means that when the joint is loaded along the limb's axis, part of that load pushes the tibia forward relative to the femur. The anterior cruciate resists it.

Clinical Relevance

Loss of the lateral meniscus matters more mechanically than loss of the medial, because the lateral meniscus was compensating for a convex surface.

The posterior slope's relationship to anterior cruciate injury is a recognised question, and the slope itself is normal anatomy. Measuring it belongs to 5.16.2.

MRCS Level

Structure and Location

Describe each plateau separately. Medial: larger surface area, oval front to back, concave in both planes, with a thicker subchondral plate. Lateral: smaller, more circular, convex sagittally, with the articular surface extending further posteriorly over the edge of the bone.

The intercondylar area is divided by the tibial spine into an anterior part, carrying the anterior cruciate and the anterior meniscal roots, and a posterior part, carrying the posterior cruciate and the posterior roots. The posterior intercondylar area descends onto the posterior surface of the bone, which is where the posterior cruciate attaches.

The articular cartilage is thicker on the plateau than on the femoral condyles, and thicker centrally, where the meniscus does not cover it, than peripherally.

Relations

Meniscal coverage: the menisci cover the peripheral part of each plateau, leaving a central uncovered area. That uncovered area is larger medially.

Peripheral attachments: the coronary or meniscotibial ligaments attach the meniscal periphery to the bone just below the articular margin, and they are shorter and tighter medially, which is why the medial meniscus is less mobile.

Posteriorly the plateau overhangs, and the popliteus tendon and the posterior capsule lie against the posterolateral margin.

The popliteal artery lies behind the posterior capsule at the level of the plateau, which is the relation that governs posterior plateau surgery.

Blood Supply and Innervation

Subchondral and metaphyseal bone is supplied by the inferior genicular arteries and the tibial recurrents, entering through the capsular and periosteal attachments around the margin.

The articular cartilage is avascular and depends on synovial fluid. The meniscal periphery is vascular and the inner part is not, which is the basis of the red and white zone distinction. 2.5.3 owns the meniscal supply.

Innervation of the plateau margin and capsule is from the articular branches of the tibial nerve posteriorly, the common peroneal recurrent branch anterolaterally and the obturator medially. The uncovered central cartilage is not innervated.

Function

Contact area on the plateau is largest near extension and decreases with flexion, because the femoral radius decreases posteriorly and because the contact point moves onto the narrower posterior part of each surface.

Constraint is asymmetrical. The medial compartment is a concave surface with a relatively fixed meniscus, so it tolerates little translation. The lateral compartment is convex with a mobile meniscus, so it permits a great deal.

Slope sets the resting direction of load transmission. Combined with the convex lateral surface, a steeper lateral slope allows more anterior translation of the lateral tibia, which is the anatomical substrate of the pivot shift. 3.7.9 owns the mechanics.

Clinical Relevance

Plateau fractures are described by which part of the surface is involved, and the distinction between the two surfaces is why medial and lateral plateau fractures behave differently.

Subchondral bone is denser medially, so a tibial component subsides differently on the two sides and so does fixation in fracture work.

Meniscal root attachments sit in the intercondylar area, not on the plateau surface, and a root avulsion is therefore a bony as well as a soft tissue problem. 2.5.7 and 2.6.4 own the roots.

The uncovered central cartilage is not innervated, which is part of why cartilage damage can be extensive before it is symptomatic.

FRCS Level

Relations

The posterior margin of the plateau and the popliteal artery are separated by capsule alone. Instrumentation that passes posteriorly from within the joint, and saw cuts that exit posteriorly, both approach that plane.

The posteromedial corner structures attach just below the margin, so a tibial cut taken low enough to clear the plateau can reach them, and the deep collateral layer is released before the superficial one is.

Function

Tibial slope is the variable a surgeon can change with the most mechanical effect per degree, and it is changed inadvertently more often than deliberately. A tibial cut taken with more or less posterior inclination than intended alters cruciate demand in a retaining knee and alters the flexion gap in any knee.

Constraint asymmetry explains why a flat tibial insert does not behave like a native plateau and why insert geometry is chosen rather than assumed.

Restoring the native obliquity of the joint line in the coronal plane is a different question from restoring slope in the sagittal plane, and the two are independent.

Clinical Relevance

In cruciate retaining arthroplasty, slope interacts with the retained ligament. In cruciate substituting designs it interacts with the post. Neither interaction is optional, and both follow from the anatomy on this page.

In slope modifying osteotomy for the failed or multiply revised cruciate, the surgical target is the feature described here. The indication and the technique belong to Section 7.

In plateau fracture surgery, restoring the articular surface and restoring the slope are separate goals that can conflict, because the surface can be reduced in a position that changes the slope.

Measurement of slope, of coronal alignment and of the relationship between them is absent from this page. It is central to all three decisions above, and decision 005 records why the numbers are not here.