Planum tibiae

The proximal or upper extremity of the tibia is expanded in the transverse plane with a medial and lateral condyle, which are both flattened in the horizontal plane.

The medial condyle is the larger of the two and is better supported over the shaft.

The upper surfaces of the condyles articulate with the femur to form the tibiofemoral joint, the weightbearing part of the kneejoint.

The medial and lateral condyle are separated by the intercondylar area, where the cruciate ligaments and the menisci attach.

Here the medial and lateral intercondylar tubercle forms the intercondylar eminence.

Together with the medial and lateral condyle the intercondylar region forms the tibial plateau, which both articulates with and is anchored to the lower extremity of the femur.

The intercondylar eminence divides the intercondylar area into an anterior and posterior part.

The anterolateral region of the anterior intercondylar area are perforated by numerous small openings for nutrient arteries.

The articular surfaces of both condyles are concave, particularly centrally.

The flatter outer margins are in contact with the menisci.

The medial condyles superior surface is oval in form and extends laterally onto the side of medial intercondylar tubercle.

The lateral condyles superior surface is more circular in form and its medial edge extends onto the side of the lateral intercondylar tubercle.

The posterior surface of the medial condyle bears a horizontal groove for part of the attachment of the semimembranosus muscle, whereas the lateral condyle has a circular facet for articulation with the head of the fibula.

Beneath the condyles is the tibial tuberosity which serves for attachment of the patellar ligament, a continuation of the quadriceps femoris muscle.

Facets

The superior articular surface presents two smooth articular facets.

The medial facet, oval in shape, is slightly concave from side to side, and from before backward.

The lateral, nearly circular, is concave from side to side, but slightly convex from before backward, especially at its posterior part, where it is prolonged on to the posterior surface for a short distance.

The central portions of these facets articulate with the condyles of the femur, while their peripheral portions support the menisci of the knee joint, which here intervene between the two bones.

Intercondyloid eminence

Between the articular facets in the intercondylar area, but nearer the posterior than the anterior aspect of the bone, is the intercondyloid eminence (spine of tibia), surmounted on either side by a prominent tubercle, on to the sides of which the articular facets are prolonged; in front of and behind the intercondyloid eminence are rough depressions for the attachment of the anterior and posterior cruciate ligaments and the menisci.

Surfaces

The anterior surfaces of the condyles are continuous with one another, forming a large somewhat flattened area; this area is triangular, broad above, and perforated by large vascular foramina; narrow below where it ends in a large oblong elevation, the tuberosity of the tibia, which gives attachment to the patellar ligament; a bursa intervenes between the deep surface of the ligament and the part of the bone immediately above the tuberosity.

Posteriorly, the condyles are separated from each other by a shallow depression, the posterior intercondyloid fossa, which gives attachment to part of the posterior cruciate ligament of the knee-joint. The medial condyle presents posteriorly a deep transverse groove, for the insertion of the tendon of the semimembranosus.

Its medial surface is convex, rough, and prominent; it gives attachment to the medial collateral ligament. The lateral condyle presents posteriorly a flat articular facet, nearly circular in form, directed downward, backward, and lateralward, for articulation with the head of the fibula.

Its lateral surface is convex, rough, and prominent in front: on it is an eminence, situated on a level with the upper border of the tuberosity and at the junction of its anterior and lateral surfaces, for the attachment of the iliotibial band.

Just below this a part of the extensor digitorum longus takes origin and a slip from the tendon of the biceps femoris is inserted.