The proximal end of the tibia is expanded in the transverse plane for weight-bearing and consists of a medial condyle and a lateral condyle, which are both flattened in the horizontal plane and overhang the shaft (Fig. 6.55).
The superior surfaces of the medial and lateral condyles are articular and separated by an intercondylar region, which contains sites of attachment for strong ligaments (cruciate ligaments) and interarticular cartilages (menisci) of the knee joint.
The articular surfaces of the medial and lateral condyles and the intercondylar region together form a “tibial plateau,” which articulates with and is anchored to the distal end of the femur. Inferior to the condyles on the proximal part of the shaft is a large tibial tuberosity and roughenings for muscle and ligament attachments.
The tibial condyles are thick horizontal discs of bone attached to the top of the tibial shaft (Fig. 6.55).
The medial condyle is larger than the lateral condyle and is better supported over the shaft of the tibia. Its superior surface is oval for articulation with the medial condyle of the femur. The articular surface extends laterally onto the side of the raised medial intercondylar tubercle.
The superior surface of the lateral condyle is circular and articulates above with the lateral condyle of the femur. The medial edge of this surface extends onto the side of the lateral intercondylar tubercle.
The superior articular surfaces of both the lateral and medial condyles are concave, particularly centrally. The outer margins of the surfaces are flatter and are the regions in contact with the interarticular discs (menisci) of fibrocartilage in the knee joint.
The nonarticular posterior surface of the medial condyle bears a distinct horizontal groove for part of the attachment of the semimembranosus muscle, and the undersurface of the lateral condyle bears a distinct circular facet for articulation with the proximal head of the fibula.
The intercondylar region of the tibial plateau lies between the articular surfaces of the medial and lateral condyles (Fig. 6.55). It is narrow centrally where it is raised to form the intercondylar eminence, the sides of which are elevated further to form medial and lateral intercondylar tubercles.
The intercondylar region bears six distinct facets for the attachment of menisci and cruciate ligaments. The anterior intercondylar area widens anteriorly and bears three facets:
The most anterior facet is for attachment of the anterior end (horn) of the medial meniscus.
Immediately posterior to the most anterior facet is a facet for the attachment of the anterior cruciate ligament.
A small facet for the attachment of the anterior end (horn) of the lateral meniscus is just lateral to the site of attachment of the anterior cruciate ligament.
The posterior intercondylar area also bears three attachment facets:
The most anterior is for attachment of the posterior horn of the lateral meniscus.
Posteromedial to the most anterior facet is the site of attachment for the posterior horn of the medial meniscus.
Behind the site of attachment for the posterior horn of the medial meniscus is a large facet for the attachment of the posterior cruciate ligament.
In addition to these six sites of attachment for menisci and cruciate ligaments, a large anterolateral region of the anterior intercondylar area is roughened and perforated by numerous small nutrient foramina for blood vessels. This region is continuous with a similar surface on the front of the tibia above the tuberosity and lies against infrapatellar connective tissue.
The tibial tuberosity is a palpable inverted triangular area on the anterior aspect of the tibia below the site of junction between the two condyles (Fig. 6.55). It is the site of attachment for the patellar ligament, which is a continuation of the quadriceps femoris tendon below the patella.
Shaft of tibia