Tibia: Encyclopedia II - Tibia - The upper extremity

Tibia - The upper extremity

('proximal extremity') The upper extremity is large, and expanded into two eminences, the medial and lateral condyles. The superior articular surface presents two smooth articular facets [Fig. 1].

• 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.

Between the articular facets, 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.

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 ligamentum patellæ; 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 tibial 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.

Adapted from the Wikipedia article "The upper extremity", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki