human anatomy, the tibia is the second largest bone next to the
femur. As in other vertebrates the tibia is one of two bones in the lower leg, the other being the fibula, and is a component of the knee and ankle joints. The leg bones (femur, tibia and fibula) are the strongest
long bones as they have to support the rest of the body.
ossification or formation of the bone starts from three centers; one in the shaft and one in each extremity.
The tibia is categorized as a
long bone and is as such composed of a
diaphysis and two
epiphyses. The diaphysis is the midsection of the tibia, also known as the
shaft or body. While the epiphyses are the two rounded extremities of the bone; an
upper (also known as superior or proximal) closest to the
thigh and a
lower (also known as inferior or distal) closest to the
. The tibia is most contracted in the lower third and the distal extremity is smaller than the proximal.
Upper surface of right tibia. (Anterior is at top.)
The proximal or upper extremity of the tibia is expanded in the transverse plane with a
lateral condyle, which are both flattened in the horizontal plane. The medial condyle is the largest 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
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
posterior part. The anterolateral region of the anterior intercondylar area are perforated by numerous small openings for
 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.
The superior articular surface presents two smooth articular
- 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 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
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
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
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.
Bones of the right leg. Anterior surface
The shaft or body of the tibia is triangular in cross-section and forms three borders: An anterior, medial and lateral or interosseous border. These three borders form three surfaces; the medial, lateral and posterior.
 The forward flat part of the tibia is called the fibia, often confused with the fibula.
The anterior crest or border, the most prominent of the three, commences above at the
tuberosity, and ends below at the anterior margin of the
medial malleolus. It is sinuous and prominent in the upper two-thirds of its extent, but smooth and rounded below; it gives attachment to the
deep fascia of the leg.
The medial border is smooth and rounded above and below, but more prominent in the center; it begins at the back part of the medial condyle, and ends at the posterior border of the medial malleolus; its upper part gives attachment to the tibial collateral ligament of the knee-joint to the extent of about 5 cm., and insertion to some fibers of the
popliteus muscle; from its middle third some fibers of the
flexor digitorum longus muscles take origin.
The interosseous crest or lateral border is thin and prominent, especially its central part, and gives attachment to the
interosseous membrane; it commences above in front of the fibular articular facet, and bifurcates below, to form the boundaries of a triangular rough surface, for the attachment of the interosseous ligament connecting the tibia and fibula.
The medial surface is smooth, convex, and broader above than below; its upper third, directed forward and medialward, is covered by the
aponeurosis derived from the tendon of the
sartorius, and by the tendons of the
Semitendinosus, all of which are inserted nearly as far forward as the anterior crest; in the rest of its extent it is
The lateral surface is narrower than the medial; its upper two-thirds present a shallow groove for the origin of the Tibialis anterior; its lower third is smooth, convex, curves gradually forward to the anterior aspect of the bone, and is covered by the tendons of the
Extensor hallucis longus, and
Extensor digitorum longus, arranged in this order from the medial side.
The posterior surface presents, at its upper part, a prominent ridge, the popliteal line, which extends obliquely downward from the back part of the articular facet for the fibula to the medial border, at the junction of its upper and middle thirds; it marks the lower limit of the insertion of the
Popliteus, serves for the attachment of the fascia covering this muscle, and gives origin to part of the
Flexor digitorum longus, and
Tibialis posterior. The triangular area, above this line, gives insertion to the Popliteus. The middle third of the posterior surface is divided by a vertical ridge into two parts; the ridge begins at the popliteal line and is well-marked above, but indistinct below; the medial and broader portion gives origin to the Flexor digitorum longus, the lateral and narrower to part of the
Tibialis posterior. The remaining part of the posterior surface is smooth and covered by the Tibialis posterior,
Flexor digitorum longus, and
Flexor hallucis longus. Immediately below the popliteal line is the nutrient foramen, which is large and directed obliquely downward.
Lower extremity of tibia seen from the front
Lower extremity of tibia seen from the back
The lower extremity of the tibia is much smaller than the upper extremity and presents five surfaces; it is prolonged downward on its medial side as a strong pyramidal process, the
medial malleolus. The lower extremity of the tibia together with the fibula and
talus forms the
The inferior articular surface is quadrilateral, and smooth for articulation with the talus. It is concave from before backward, broader in front than behind, and traversed from before backward by a slight elevation, separating two depressions. It is continuous with that on the medial malleolus.
The anterior surface of the lower extremity is smooth and rounded above, and covered by the tendons of the Extensor muscles; its lower margin presents a rough transverse depression for the attachment of the articular capsule of the ankle-joint.
The posterior surface is traversed by a shallow groove directed obliquely downward and medialward, continuous with a similar groove on the posterior surface of the talus and serving for the passage of the tendon of the
Flexor hallucis longus.
The lateral surface presents a triangular rough depression for the attachment of the inferior interosseous ligament connecting it with the fibula; the lower part of this depression is smooth, covered with cartilage in the fresh state, and articulates with the fibula. The surface is bounded by two prominent borders (the
anterior and posterior colliculi), continuous above with the
interosseous crest; they afford attachment to the anterior and posterior ligaments of the lateral malleolus.
The medial surface -- see
medial malleolus for details.
Ankle fractures of the tibia have several classification systems based on location or mechanism:
The tibia is supplied with blood from two sources: A
nutrient artery, as the main source, and
periosteal vessels derived from the
anterior tibial artery.
The tibia is a part of four joints; the knee, ankle,
inferior tibiofibular joint.
In the knee the tibia forms one of the two
articulations with the
femur, often referred to as the tibiofemoral components of the knee joint.
 This is the weightbearing part of the knee joint.
 The tibiofibular joints are the articulations between the tibia and fibula which allows very little movement. The
proximal tibiofibular joint is a small
plane joint. The joint is formed between the undersurface of the
lateral tibial condyle and the
head of fibula. The
joint capsule is reinforced by
posterior ligament of the head of the fibula.
distal tibiofibular joint (tibiofibular syndesmosis) is formed by the rough, convex surface of the medial side of the distal end of the fibula, and a rough concave surface on the lateral side of the tibia.
 The part of the ankle joint known as the talocrural joint, is a
hinge joint that connects the distal ends of the tibia and fibula in the lower limb with the proximal end of the talus. The articulation between the tibia and the talus bears more weight than between the smaller fibula and the talus.
Plan of ossification of the tibia. From three centers.
Epiphysial lines of tibia and fibula in a young adult. Anterior aspect.
The tibia is
ossified from three
primary center for the
diaphysis (shaft) and a secondary center for each
epiphysis (extremity). Ossification begins in the center of the body, about the seventh week of fetal life, and gradually extends toward the extremities.
The center for the upper epiphysis appears before or shortly after birth at close to 34 weeks gestation; it is flattened in form, and has a thin tongue-shaped process in front, which forms the
tuberosity; that for the lower epiphysis appears in the second year.
The lower epiphysis fuses with the tibial shaft at about the eighteenth, and the upper one fuses about the twentieth year.
Two additional centers occasionally exist, one for the tongue-shaped process of the upper epiphysis, which forms the tuberosity, and one for the