Attachments on the Medial Condyle

(a) The semimembranosus is inserted into the groove on the posterior surface.

(b) The capsular ligament of the knee joint is attached to the upper border, which also gives attachment to the deeper fibres of the tibial collateral ligament (Fig. 12.9).

(c) The medial patellar retinaculum is attached to the anterior surface.

2. Attachments on Lateral Condyle fO^f Attacnmenfsontne Intercondylar Area

(a) The iliotibial tract is attached to the flatteneck-^f The following are attached from before backwards.

impression on the anterior surface. , . _. , ._, , „,, ,. '

^ (a) The anterior horn of the medial meniscus, just

(b) The capsular ligament of the superior in front of the medial articular surface (Fig. 2.30).

tibiofibular joint is attached around the margins of

the fibular facet ^ ^^neanterlor cruciate ligament on a smooth

area just behind the previous attachment.

(c) The origins of the extensor digitorum longus

and of the peroneus longus extend on to the lateral (c) The anterior horn of the lateral meniscus, to condyle near the fibular facet. the front of the intercondylar eminence, and lateral

, ^ , , , to the anterior cruciate ligament (Fig. 12.13).

(d) The groove on the posterior surface of the

lateral condyle is occupied by the tendon of the (d) The posterior horn of the lateral meniscus, to popliteus with a bursa intervening. the posterior slope of the intercondylar eminence.

Mmmmmmmmmmmmmm

(e) The posterior horn of the medial meniscus, to the depression behind the base of the medial intercondylar tubercle.

(f) The posterior cruciate ligament, to the posterior- most smooth areaP

4. Attachment on Tibial Tuberosity

The ligamentum patellae is attached to the upper smooth part of the tibial tuberosity. The lower rough area of the tuberosity is subcutaneous, but is separated from the skin by the subcutaneous infrapatellar bursa (Fig. 3.7).

5. Attachment on the Shaft

(a) The tibialis anterior arises from the upper two-thirds or less of the lateral surface (Fig. 2.33).

(b) The upper part of the medial surface receives the insertions of the sartorius, the gracilis and the semitendinosus, from before backwards (Fig. 2.34). Still further posteriorly this surface gives attachment

to the tibial collateral ligament along the media border.

(c) The soleus arises from the soleal line (Fig. 2.32) The soleal line also gives attachment to the fascis covering the soleus, the fascia covering the popliteus, and the transverse fascial septum. The tendinous arch for origin of the soleus is attached to a tubercle at the upper end of the soleal line.

(d) The popliteus is inserted on the posterior surface, into the triangular area above the soleal

(e) The medial area of the posterior surface below the soleal line gives origin to the flexor digitorum longus while the lateral area gives origin to the tibialis posterior.

(f) The anterior border of the tibia gives attachment to the deep fascia of the leg and, in its lower part, to the superior extensor retinaculum.

(g) The rough upper part of the fibular notch gives attachment to the interosseous tibiofibular ligament.

(h) The capsular ligament of the ankle joint is attached to the lower end along the margins of the articular surface. The deltoid ligament of the ankle joint is attached to the lower border of the medial malleolus (Figs 12.16, 2.28).

Relations of the Tibia

Apart from the relations mentioned above, the following may be noted.

(a) The lower part of the anterior surface of the shaft, and the anterior aspect of the lower end, are crossed from medial to lateral side by the tibialis anterior, the extensor hallucis longus, the anterior tibial artery, the deep peroneal nerve, the extensor digitorum longus, and the peroneus tertius (Fig. 2.31).

(b) The lowermost part of the posterior surface of the shaft and the posterior aspect of the lower end are related from medial to lateral side to the tibialis posterior, which lies in a groove, the flexor digitorum longus, the posterior tibial artery, the tibial nerve, and the flexor hallucis longus. The groove for the tendon of the tibialis posterior continues downwards on the posterior surface of the medial malleolus.

(c) The lower one-third of the medial surface of the shaft is crossed by the great saphenous vein (Fig. 8.2).

Blood Supply

The nutrient artery to the tibia is the largest nutrient artery in the body. It is a branch of the posterior tibial artery which enters the bone on its posterior surface.

Ossification: The tibia ossifies from one primary and two secondary centres. The primary centre appears in the shaft during the seventh week of intrauterine life. A secondary centre for the upper end appears just before birth, and fuses with the shaft at 16-18 years. The upper epiphysis usually includes the tibial tuberosity. A secondary centre for the lower end appears during the first year, forms the medial malleolus by the seventh year, and fuses with the shaft by 15-17 years. Separate secondary centres may appear for the tibial tuberosity and the medial malleolus (Fig. 2.35).

CLINICAL ANATOMY

1. The upper end of the tibia is one of the commonest sites for acute osteomyelitis. The knee joint remains safe because the capsule is attached near the articular margins of the tibia, proximal to the epiphyseal line.

2. The tibia is commonly fractured at the junction of the upper two-thirds and the lower one-third of the shaft as the shaft is most slender here. Such fractures may unite slowly, or may not unite at all (non-union) as the blood supply to this part of the bone is poor.

This may also be caused by tearing of the nutrient artery.

3. Sometimes a surgeon takes a piece of bone from the part of the body and uses it to repair a defect in some other bone called a bone graft. For this purpose pieces of bone are easily obtained from the subcutaneous medM aspect of the tibia.

4. If the foot gets caught in a hole in the ground there may be forcible abduction and external rotation.

In such an injury, first there occurs a spiral fracture of the lateral malleolus, then avulsion of the tibial collateral ligament and, finally, the posterior margin of the lower end of the tibia shears off against the talus. These stages are termed 1st, 2nd and 3rd degrees of Pott's fracture. Forward dislocation of the tibia on the talus produces the characteristic prominence of the heel in this injury. This is the commonest type of the fracture at the ankle.

_________________ FIBULA ________________

The fibula is the lateral and smaller bone of the leg. It is very thin as compared to the tibia. It is homologous with the ulna of the upper limb.

Side Determination

1. The upper end, or head, is slightly expanded in all directions. The lower end or lateral malleolus is expanded anteroposteriorly and is flattened from side to side.

2. The medial side of the lower end bears a triangular articular facet anteriorly, and a deep or malleolar fossa posteriorly.

Features

The fibula has an upper end, a shaft and a lower end.

Upper End or Head

It is slightly expanded in all directions. The superior surface bears a circular articular facet which articulates with the lateral condyle of the tibia. The apex of the head or the styloid process projects upwards from its posterolateral aspect.

The constriction immediately below the head is known as the neck of the fibula (Figs 2.36, 2.37A).

Shaft

The shaft shows considerable variation in its form because it is moulded by the muscles attached to it. It has three borders—anterior, posterior and interosseous; and three surfaces—medial, lateral and posterior.

Borders

The anterior border begins just below the anterior aspect of the head. At its lower end it divides to enclose an elongated triangular area which is continuous with the lateral surface of the lateral malleolus.

The posterior border is rounded. Its upper end lies in line with the styloid process. Below, the border is continuous with the medial margin of the groove on the back of the lateral malleolus.

The interosseous or medial border lies just medial to the anterior border, but on a more posterior plane. It terminates below at the upper end of a roughened area above the talar facet of the lateral malleolus. In its upper two-thirds, the interosseous border lies very close to the anterior border and may be indistinguishable from it.

Surfaces

The medial surface lies between the anterior and interosseous borders. In its upper two-thirds, it is very narrow, measuring 1 mm or less (Fig.2.37B).

The lateral surface lies between the anterior and posterior borders. It is twisted backwards in its lower part (Fig.2.37B).

The posterior surface is the largest of the three surfaces. It lies between the interosseous and posterior borders. In its upper two-thirds, it is divided into two parts by a vertical ridge called the medial crest.

Lower End or Lateral Malleolus

The tip of the lateral malleolus is 0.5 cm lower than that of the medial malleolus, and its anterior surface is 1.5 cm posterior to that of the medial malleolus. It has the

ATTACHMENTS AND RELATIONS OF THE FIBULA 1. The medial surface of the shaft gives origin to: (a) The extensor digitorum longus, from the whole of the upper one-fourth, and from the anterior half of the middle two-fourths; (b) the extensor hallucis longus, from the posterior half of its middle two-fourths; and (c) the peroneus tertius, from its lower one-fourth (Figs 2.36, 2.38).

2. The part of the posterior surface between the medial crest and the interosseous border, the grooved part, gives origin to the tibialis posterior.

3. The part of the posterior surface between the medial crest and the posterior border gives origin to: (a) the soleus from the upper one-fourth and (b) the flexor hallucis longus from its lower three-fourths (Figs 2.39, 2.40).

4. The lateral surface of the shaft gives origin to:

(a) the peroneus longus, from its upper one-third, and the posterior half of the middle one-third; and

(b) the peroneus brevis from the anterior half of its middle one-third, and the whole of the lower one-third.

The common peroneal nerve terminates in relation to the neck of fibula (Figs 2.41, 2.42).

5. The head of the fibula receives the insertion of longus, and the soleus, described above, extend on to the corresponding aspects of the head.

6. The capsular ligament of the superior tibio fibular joint is attached around the articular facet.

Fig. 2.36: Right fibula. Anterior aspect.

7. The anterior border of the fibula gives attachment to: (a) the anterior intermuscular septum of the leg;

(b) the superior extensor retinaculum, to the lower part of the anterior margin of the triangular area; and (c) the superior peroneal retinaculum, to the lower part of the posterior margin of the triangular area.

8. The posterior border gives attachment to the posterior intermuscular septum.

9. The interosseous border gives attachment to the interosseous membrane. The attachment leaves

Fig. 2.37: Right fibula. Posterior aspect.

a gap at the upper end for passage of the anterior tibial vessels (Fig. 2.28).

10. The triangular area above the medial surface of the lateral malleolus gives attachment to (a) the interosseous tibiofibular ligament, in the middle;

(b) the anterior tibiofibular ligament, anteriorly; and (c) the posterior tibiofibular, posteriorly (Figs 12.16, 2.28).

11. The attachments on the lateral malleolus are as follows.

(a) anterior talofibular ligaments to the anterior and posterior surfaces; (b) inferior transverse tibiofibular ligament above and posterior talofibular ligament below to the malleolar fossa; (c) The capsule of the ankle joint along the edges of the malleolar articular surface; and (d) slight notch on the lower border gives attachment to calcaneofibular ligament (Figs 2.28, 12.20, 12.21).

12. The groove on the posterior surface of the malleolus lodges the tendon of the peroneus brevis, which is deep, and of the peroneus longus, which is superficial (Fig. 2.37A).

Blood Supply

The peroneal artery gives off the nutrient artery for the fibula, which enters the bone on its posterior surface.

Ossification: The fibula ossifies from one primary and two secondary centres. The primary centre for the shaft appears during the eighth week of intrauterine life.

A secondary centre for the lower end appears during the first year, and fuses with the shaft by about sixteen years.

A secondary centre for the upper end appears during the fourth year, and fuses with the shaft by about eighteen years (Fig. 2.35).

The fibula violates the law of ossification because the secondary centre which appears first in the lower end does not fuse last. The reasons for this violation are: (1) the secondary centre appears first in the lower end because it is a pressure epiphysis; and (2) the upper epiphysis fuses last because this is the growing end of the bone.

CLINICAL ANATOMY

1. The upper and lower ends of the fibula are subcutaneous and palpable.

2. The common peroneal nerve can be rolled against the neck of the fibula. This nerve is commonly injured here.

3. In the first stage of Pott's fracture, the lower end of the fibula is fractured spirally.

4. The fibula is an ideal spare bone for a bone graft.

5. Though it does not bear any weight, the lateral malleolus and the ligaments attached to it are very important in maintaining stability at the ankle joint.