4: The Lower Limb

Surface anatomy and surface markings of the lower limb

Anatomically the upper and lower limbs are comparable to each other as regards the arrangement of the bones, joints, main muscle groups, vessels and nerves. However, compared with the complex movements of the upper limb, designed to place the hand in a multiplicity of positions, together with the intricate and multiple functions of the hand, fingers and thumb, the functions of the lower limb are simple indeed – first, to act as a rigid column in the standing position and, second, to turn into a lever system when the subject walks or runs. As with the upper limb, several aspects of the important clinical anatomy of the lower limb can be examined, reviewed and revised on yourself, your colleagues or your patients.

Bones and joints

The tip of the anterior superior spine of the ilium is easily felt and may be visible in the thin subject. The greater trochanter of the femur lies a hand’s breadth below the iliac crest; it is best palpated with the hip passively abducted so that the overlying hip abductors (tensor fasciae latae and gluteus medius and minimus) are relaxed. In the very thin patient, the greater trochanter may be seen as a prominent bulge and its overlying skin is a common site for a pressure sore to form in such a case.

The ischial tuberosity is covered by gluteus maximus when one stands. In the sitting position, however, the muscle slips away laterally so that weight is taken directly on the bone. To palpate this bony point, therefore, feel for it uncovered by gluteus maximus in the flexed position of the hip.

At the knee, the patella forms a prominent landmark. When quadriceps femoris is relaxed, this bone is freely mobile from side to side; note that this is so when you stand erect. The condyles of the femur and tibia, the head of the fibula and the joint line of the knee are all readily palpable; less so is the adductor tubercle of the femur, best identified by running the fingers down the medial side of the thigh until they are halted by it, the first bony prominence so to be encountered.

The tibia can be felt along the entire length of its anterior subcutaneous border from the tibial tuberosity above, which marks the insertion of the quadriceps tendon, to the medial malleolus at the ankle. The subcutaneous surface of the tibia, which can be felt immediately medial to its subcutaneous border, is crossed by two structures – the long saphenous vein, which is readily visible immediately in front of the medial malleolus of the tibia, and the adjacent saphenous nerve. The head of the fibula, as noted previously, is easily palpable; note that it lies below and towards the posterior part of the lateral tibial condyle. Distal to its neck, the fibula ‘disappears’ as it dives into the muscle mass of the peroneal muscles, becoming subcutaneous distally. The fibula is subcutaneous for its terminal 7 cm (3 in) above the lateral malleolus. The latter extends more distally than the stumpier medial malleolus of the tibia.

Immediately in front of the malleoli can be felt a block of bone which is the head of the talus. Feel it move up and down in dorsiflexion and plantarflexion of the ankle.

The tuberosity of the navicular stands out as a bony prominence 2.5 cm (1 in) in front of the medial malleolus; it is the principal point of insertion of tibialis posterior. The base of the 5th metatarsal is easily felt on the lateral side of the foot and is the site of insertion of peroneus brevis.

If the calcaneus (os calcis) is carefully palpated, the peroneal tubercle can be felt 2.5 cm (1 in) below the tip of the lateral malleolus and the sustentaculum tali 2.5 cm (1 in) below the medial malleolus; these represent pulleys, respectively, for peroneus longus and for flexor hallucis longus.

Bursae of the lower limb

A number of the bony prominences described in the previous section are associated with overlying bursae, which may become distended and inflamed: the one over the ischial tuberosity may enlarge with too much sitting (‘weaver’s bottom’); that in front of the patella is affected by prolonged kneeling forwards, as in scrubbing floors or hewing coal (‘housemaid’s knee’, the ‘beat knee’ of north‐country miners, or prepatellar bursitis); whereas the bursa over the ligamentum patellae is involved by years of kneeling in a more erect position – as in praying (‘clergyman’s knee’ or infrapatellar bursitis). Young women who wear fashionable but tight shoes are prone to bursitis over the insertion of the Achilles tendon (calcaneal tendon or tendo calcaneus) into the calcaneus and may also develop bursae over the navicular tuberosity and dorsal aspects of the phalanges.

A ‘bunion’ is a thickened bursa on the inner aspect of the first metatarsal head, usually associated with hallux valgus deformity. Note that the bursae that may develop (and become inflamed) over the calcaneus, navicular, the phalanges and the head of the first metatarsal are called adventitial bursae. They are not found in normal anatomy but occur only under the pathological conditions described. This is in contrast to the pre‐ and infrapatellar bursae, which are normal anatomical structures and which may become distended with fluid as a result of repeated trauma.

Mensuration in the lower limb

Measurement is an important part of the clinical examination of the lower limb. Unfortunately, students find difficulty in carrying this out accurately and still greater difficulty in explaining and interpreting the results they obtain, yet this is nothing more or less than a simple exercise in applied anatomy.

First note the differences between real and apparent shortening of the lower limbs. Real shortening is due to actual loss of bone length; for example, when a femoral fracture has united with a good deal of overriding of the two fragments. Apparent shortening is due to a fixed deformity of the limb (Fig. 147). Stand up and flex your knee and hip on one side, imagine these are both ankylosed at 90° and note that, although there is no loss of tissue in this limb, it is apparently some 60 cm (2 ft) shorter than its partner.

Image described by caption. — **Fig. 147** Apparent shortening – one limb may be apparently shorter than the other because of fixed deformity; the legs in this illustration are actually equal in length but the right is *apparently* considerably shorter because of a gross flexion contracture at the hip. Apparent shortening is measured by comparing the distance from the umbilicus to the medial malleolus on each side.

If there is a fixed pelvic tilt or fixed joint deformity in one limb, there may be this apparent difference between the lengths of the two limbs. By experimenting on yourself you will find that adduction apparently shortens the limb, whereas it is apparently lengthened in abduction.

To measure the real length of the limbs (Fig. 148), overcome any disparity due to fixed deformity by putting both limbs into exactly the same position; where there is no joint fixation, this means that the patient lies with his pelvis ‘square’, his limbs abducted symmetrically and both limbs lying flat on the couch. If, however, one hip is in 60° of fixed flexion, for example, the other hip must first be put into this identical position. The length of each limb is then measured from the anterior superior iliac spine to the medial malleolus. In order to obtain identical points on each side, slide the finger upwards along Poupart’s inguinal ligament and mark the bony point first encountered by the finger. Similarly, slide the finger upwards from just distal to the malleolus to determine the apex of this landmark on each side.

A patient having one lower limb shorter than the other. The patient lies with the pelvis “square” and the legs placed symmetrically, with dashed lines from anterior superior iliac spine to medial malleolus. — **Fig. 148** Measuring real shortening – the patient lies with the pelvis ‘square’ and the legs placed symmetrically. Measurement is made from the anterior superior spine to the medial malleolus on each side.

To determine apparent shortening, the patient lies with his legs parallel (as they would be when he stands erect) and the distance from umbilicus to each medial malleolus is measured (Fig. 147).

Now suppose we find 10 cm (4 in) of apparent shortening and 5 cm (2 in) of real shortening of the limb; we interpret this as meaning that 5 cm (2 in) of the shortening is due to true loss of limb length and another 5 cm (2 in) is due to fixed postural deformity.

If the apparent shortening is less than the real, this can only mean that the hip has ankylosed in the abducted, and hence apparently elongated, position.

Note this important point: one reason why the orthopaedic surgeon immobilizes a tuberculous hip in the abducted position is that, when the hip becomes ankylosed, shortening due to actual destruction at the hip (i.e. true shortening) will be compensated, to a considerable extent, by the apparent lengthening produced by the fixed abduction.

Having established that there is real shortening present, the examiner must then determine whether this is at the hip, the femur or the tibia, or at a combination of these sites.

At the hip

Place the thumb on the anterior superior spine and the index finger on the greater trochanter on each side; a glance is sufficient to tell if there is any difference between the two sides.

Measuring Nelaton’s line and Bryant’s triangle is seldom undertaken in clinical practice these days. Nevertheless, some examiners remain inclined to asking questions about them (Fig. 149).

Image described by caption and surrounding text. — **Fig. 149** (a) Nelaton’s line joins the anterior superior iliac spine to the ischial *tuberosity* – normally this passes above the greater trochanter. (b) Bryant’s triangle – in the supine subject, drop a vertical from each superior spine; compare the perpendicular distance from this line to the greater trochanter on either side. (There is no need to complete the third side of the triangle.)

Nelaton’s line joins the anterior superior iliac spine to the ischial tuberosity and should normally lie above the greater trochanter; if the line passes through or below the trochanter, there is shortening at the head or neck of the femur.

Bryant’s triangle might be better termed ‘Bryant’s T’ because it is not necessary to construct all of its three sides. With the patient supine, a perpendicular is dropped from each anterior superior spine and the distance between this line and the greater trochanter compared on each side. (The third side of the triangle, joining the trochanter to the anterior spine, need never be completed.)

At the femur

Measure the distance from the anterior superior spine (if hip disease has been excluded) or from the greater trochanter to the line of the knee joint (not to the patella, whose position can be varied by contraction of the quadriceps).

At the tibia

Compare the distance from the line of the knee joint to the medial malleolus on each side.

Muscles and tendons

Quadriceps femoris forms the prominent muscle mass on the anterior aspect of the thigh; its insertion into the medial aspect of the patella can be seen to extend more distally than on the lateral side. In the well‐developed subject, sartorius can be defined when the hip is flexed and externally rotated against resistance. It extends from the anterior superior iliac spine to the medial side of the upper end of the tibia. It forms the lateral border of the femoral triangle, and is an important landmark.

Gluteus maximus forms the bulk of the buttock and can be felt to contract in extension of the hip.

Gluteus medius and minimus and the adductors can be felt to tighten, respectively, in resisted abduction and adduction of the hip.

Define the tendons around the knee joint with the joint comfortably flexed to about 90°:

laterally – the biceps tendon passes to the head of the fibula, the iliotibial tract lies approximately 1.25 cm (0.5 in) in front of this tendon and passes to a tubercle on the anterior aspect of the lateral condyle of the tibia;
medially – the bulge which one feels is the semimembranosus insertion on which two tendons, gracilis, medially and more anteriorly, and semitendinosus, laterally and more posteriorly, are readily palpable. posteriorly – between the tendons of biceps and semitendinosus can be felt the heads of origin of gastrocnemius. This muscle, with soleus, forms the bulk of the posterior bulge of the calf; the two end distally in the Achilles tendon (calcaneal tendon).

At the front of the ankle (Fig. 150) the tendon of tibialis anterior lies most medially, passing to its insertion at the base of the first metatarsal and the medial cuneiform. More laterally, the tendons of extensor hallucis longus and extensor digitorum longus are readily visible in the dorsiflexed foot. Peroneus longus and brevis tendons pass behind the lateral malleolus. The tendon of peroneus tertius can be felt on careful palpation on the lateral aspect of the dorsum of the foot as this tendon passes to the base of the 5th metatarsal. This is of more than academic interest (Fig. 150). Peroneus tertius is present only in the human. Only humans stand on the whole sole of the foot; lower mammals stand and walk on tiptoe. Presumably peroneus tertius has evolved in humans as a detachment from the lateral aspect of extensor digitorum longus to assist in the development of the plantigrade human foot. Behind the medial malleolus, working from the medial to the lateral side, lie the tendons of tibialis posterior and flexor digitorum longus, the posterior tibial artery with its venae comitantes, the tibial nerve and, finally, flexor hallucis longus (Fig. 151).

Anterior aspect of right ankle displaying the structures passing over the dorsum, with lines marking the peroneus tertius, dorsalis pedis artery, extensor halluces longus, extensor digitorum longus and brevis. — **Fig. 150** The structures passing over the dorsum of the ankle (right ankle, anterior aspect).

Medial aspect of the right ankle displaying the depicting the structures passing behind the medial malleolus, with lines marking the posterior tibial vein, nerve, and artery, flexor digitorum longus, etc. — **Fig. 151** The structures passing behind the medial malleolus (right ankle, medial aspect).

Vessels

The femoral artery (Fig. 152) can be felt pulsating at the mid‐inguinal point, halfway between the anterior superior iliac spine and the pubic symphysis. The upper two‐thirds of a line joining this point to the adductor tubercle, with the hip somewhat flexed, abducted and externally rotated, accurately indicates the surface marking of this vessel. A finger on the femoral pulse lies directly over the head of the femur, immediately lateral to the femoral vein (and the termination of the great saphenous vein) and a finger’s breadth medial to the femoral nerve.

Diagram of the hip bone and femur depicting the surface markings of the femoral artery, with lines marking the adductor tubercle, popliteal artery, midline, inguinal ligament, anterior superior iliac spine, etc. — **Fig. 152** The surface markings of the femoral artery; the upper two‐thirds of a line joining the mid‐inguinal point (halfway between the anterior superior iliac spine and the symphysis pubis) to the adductor tubercle.

The pulse of the popliteal artery is often not easy to detect. It is most readily felt with the subject prone, the subject’s knee flexed and muscles relaxed. The pulse is sought by firm pressure downwards and forwards against the popliteal surface of the femur.

The pulse of dorsalis pedis (Fig. 150) is felt between the tendons of extensor hallucis longus and extensor digitorum longus on the dorsum of the foot – it is absent in approximately 2% of normal subjects. The posterior tibial artery (Fig. 151) may be felt a finger’s breadth below and behind the medial malleolus. In approximately 1% of healthy subjects this artery is replaced by the peroneal (fibular) artery.

The absence of one or both pulses at the ankle is not, therefore, in itself diagnostic of vascular disease.

The small (or short) saphenous vein commences as a continuation of the lateral limb of the subcutaneous venous network on the dorsum of the foot, runs proximally behind the lateral malleolus, and terminates by draining into the popliteal vein behind the knee. The great (or long) saphenous vein arises as a continuation of the medial limb of the dorsal network of veins and passes proximally in front of the medial malleolus, with the saphenous nerve anterior to it, to enter the femoral vein in the groin, 2.5 cm (1 in) below the inguinal ligament and immediately medial to the femoral pulse.

These veins are readily studied in any patient with extensive varicose veins and are usually visible, in their lower part, in the thin normal subject on standing. (The word ‘saphenous’ is derived from the Greek for ‘clear’.)

From the practical point of view, the position of the long saphenous vein immediately in front of the medial malleolus is a most important anatomical relationship; no matter how collapsed or obese, or how young and tiny the patient, the vein can be relied upon to be available at this site when urgently required for transfusion purposes (Fig. 153).

Nerves

Only one nerve is easily felt in the lower limb; this is the common peroneal (fibular) nerve, which can be rolled against the bone as it winds round the neck of the fibula (Fig. 154). Not unnaturally, it may be injured at this site in adduction injuries to the knee or compressed by a tight plaster cast or firm bandage, with a resultant foot drop and inversion (talipes equinovarus; see page 271).

Lateral aspect of the right knee with lines marking the lateral collateral ligament, biceps tendon, common peroneal nerve, deep peroneal nerve, and superficial peroneal nerve. — **Fig. 154** The close relationship of the common peroneal nerve to the neck of the fibula; at this site it may be compressed by a tight bandage or plaster cast (right knee, lateral aspect).

The femoral nerve emerges from under the inguinal ligament 1.25 cm (0.5 in) lateral to the femoral pulse. After a course of approximately 5 cm (2 in) the nerve breaks up into its terminal branches.

The surface markings of the sciatic nerve (Fig. 155) can be represented by a line which commences at a point midway between the posterior superior iliac spine (identified by the overlying sacral dimple) and the ischial tuberosity, curves outwards and downwards through a point midway between the greater trochanter and ischial tuberosity and then continues vertically downwards in the midline of the posterior aspect of the thigh. The nerve ends at a variable point above the popliteal fossa by dividing into the tibial and common peroneal nerves, respectively.

It would seem inconceivable that a nerve with such constant and well‐defined landmarks could be damaged by intramuscular injections, yet this has happened so frequently that it has seriously been proposed that this site should be prohibited. The explanation is, we believe, a psychological one. The standard advice is to use the upper outer quadrant of the buttock for these injections, and when the full anatomical extent of the buttock – extending upwards to the iliac crest and outwards to the greater trochanter – is implied, perfectly sound and safe advice this is. Many health‐care professionals, however, have an entirely different mental picture of the buttock; a much smaller and more aesthetic affair comprising merely the hillock of the natus. An injection into the upper outer quadrant of this diminutive structure lies in the immediate vicinity of the sciatic nerve!

A better surface marking for the ‘safe area’ of buttock injections can be defined as that area which lies under the outstretched hand when the thumb and thenar eminence are placed along the iliac crest with the tip of the thumb touching the anterior superior iliac spine (Fig. 156).

Lateral view of the pelvic bone and femur with a shaded zone representing the safe area for injections in the buttock and lines marking the greater trochanter, sciatic nerve, sacrum, iliac crest, etc. — **Fig. 156** The ‘safe area’ for injections in the buttock.

The bones and joints of the lower limb

The os innominatum

See ‘the pelvis’, pages 129–133.

The femur (Figs 157, 158)

The femur is the longest bone in the body. It is 45 cm (18 in) in length, a measurement it shares with the vas, the spinal cord and the thoracic duct and which is also the distance from the teeth to the cardia of the stomach.

Anterior aspect of the right hip bone and femur with lines marking the lateral condyle, adductor tubercle, medial condyle, articular surface for patella, neck of femur, head of femur, iliac crest, etc. — **Fig. 157** The anterior aspect of the right femur.

Posterior aspect of the right hip bone and femur with lines marking the adductor tubercle, intercondylar fossa, lateral epicondyle, linea aspera, spiral line, ischial tuberosity, lesser sciatic notch, etc. — **Fig. 158** The posterior aspect of the right femur.

The femoral head is two‐thirds of a sphere and faces upwards, medially and forwards. It is covered with articular hyaline cartilage except for its central fovea, where the ligamentum teres is attached.

The neck is 5 cm (2 in) long and is set at an angle of 135° to the shaft. In the female, with her wider pelvis, the angle is smaller.

The junction between the neck and the shaft is marked anteriorly by the trochanteric line, laterally by the greater trochanter, medially and somewhat posteriorly by the lesser trochanter and posteriorly by the prominent trochanteric crest, which unites the two trochanters.

The blood supply to the femoral head is derived from vessels travelling up from the diaphysis along the cancellous bone, from vessels in the hip capsule, where this is reflected onto the neck in longitudinal bands or retinacula, and from the artery in the ligamentum teres; this third source is negligible in adults, but essential in children, when the femoral head is separated from the neck by the cartilage of the epiphyseal line (Fig. 159).

The femoral shaft is roughly circular in section at its middle but is flattened posteriorly at each extremity. Posteriorly also it is marked by a strong crest, the linea aspera. Inferiorly, this crest splits into the medial and lateral supracondylar lines, leaving a flat popliteal surface between them. The medial supracondylar line ends distally in the adductor tubercle.

The lower end of the femur bears the prominent condyles, which are separated by a deep intercondylar notch (fossa) posteriorly but which blend anteriorly to form an articular surface for the patella. The lateral condyle is the more prominent of the two and acts as a buttress to assist in preventing lateral displacement of the patella.

CLINICAL FEATURES

The upper end of the femur is a common site for fracture in the elderly. The neck may break immediately beneath the head (subcapital), near its midpoint (midcervical) or adjacent to the trochanters (basicervical), or the fracture line may pass between, along or just below the trochanters (Fig. 160).
$Head and neck of the femur with lines marking the subcapital, pertrochanteric, cervical, and basal fracture sites.$

Fig. 160 The head and neck of the femur, showing the terminology of the common fracture sites.

Fractures of the femoral neck will interrupt completely the blood supply from the diaphysis and, should the retinacula also be torn, avascular necrosis of the head will be inevitable. The nearer the fracture to the femoral head, the more tenuous the retinacular blood supply and the more likely it is to be disrupted.

Avascular necrosis of the femoral head in children is seen in Perthes’ disease and in severe slipped femoral epiphysis; both resulting from thrombosis of the artery of the ligamentum teres.

In contrast, pertrochanteric fractures, being outside the joint capsule, leave the retinacula undisturbed; avascular necrosis, therefore, does not follow such injuries (Fig. 161).
$Left: Femoral head and neck having a pertrochanteric fracture. Right: Femoral head and neck having a subcapital fracture cutting off most of the retinacular supply to the head.$

Fig. 161 (a) A pertrochanteric fracture does not damage the retinacular blood supply – aseptic bone necrosis does not occur. (b) A subcapital fracture cuts off most of the retinacular supply to the head – aseptic bone necrosis is common. Note that the blood supply via the ligamentum teres is negligible in adult life.

There is a curious age pattern of hip injuries: children may sustain greenstick fractures of the femoral neck; schoolboys may displace the epiphysis of the femoral head; in adult life the hip dislocates; and in old age fracture of the neck of the femur again becomes the usual lesion.
Fractures of the femoral shaft are accompanied by considerable shortening as a result of the longitudinal contraction of the extremely strong surrounding muscles.

The proximal segment is flexed by iliacus and psoas and abducted by gluteus medius and minimus, whereas the distal segment is pulled medially by the adductor muscles. Reduction requires powerful traction, to overcome the shortening, and then manipulation of the distal fragment into line with the proximal segment; the limb must therefore be abducted and also pushed forwards by using a large pad behind the knee.

Fractures of the lower end of the shaft, immediately above the condyles, are relatively rare; fortunately so, because they can be extremely difficult to treat since the small distal fragment is tilted backwards by gastrocnemius, the only muscle which is attached to it. The sharp proximal edge of this distal fragment may also tear the popliteal artery, which lies directly behind it (Fig. 162).

Fig. 162 The deformities of femoral shaft fractures. (a) Fracture of the proximal shaft – the proximal fragment is flexed by iliacus and psoas and abducted by gluteus medius and minimus. (b) Fracture of the mid‐shaft – flexion of the proximal fragment by iliacus and psoas. (c) Fracture of the distal shaft – the distal fragment is angulated backwards by gastrocnemius; the popliteal artery may be torn in this injury. (In all these fractures overriding of the bone ends is produced by muscle spasm.)
The angle subtended by the femoral neck to the shaft may be decreased, producing a coxa vara deformity. This may result from adduction fractures, slipped femoral epiphysis or bone‐softening diseases. Coxa valga, in which the angle is increased, is much rarer but occurs in impacted abduction fractures. Note, however, that in children the normal angle between the neck and shaft is approximately 160°.

The patella

The patella is a sesamoid bone, the largest in the body, in the expansion of the quadriceps tendon. The tendon continues from the apex of the bone as the ligamentum patellae.

The posterior surface of the patella is covered with cartilage and articulates with the two femoral condyles by means of a larger lateral and smaller medial facet.

Occasionally the patella is bipartite, with a small, separate supero‐lateral portion. Usually this anomaly is bilateral. This may be mistaken radiologically by the inexperienced clinician as a fracture.

CLINICAL FEATURES

Lateral dislocation of the patella is resisted by the prominent, anteriorly projecting articular surface of the lateral femoral condyle and by the medial pull of the lowermost fibres of vastus medialis, which insert almost horizontally along the medial margin of the patella. If the lateral condyle of the femur is underdeveloped, or if there is a considerable genu valgum (knock‐knee deformity), recurrent dislocations of the patella may occur (Fig. 163).

Fig. 163 Factors in the stability of the patella: (a) the medial pull of vastus medialis and (b) the high patellar articular surface of the lateral femoral condyle. These resist the tendency for lateral displacement of the patella, which results from the valgus angulation between the femur and the tibia.
A direct blow on the patella may split or shatter it but the fragments are not avulsed because the quadriceps expansion remains intact.

The patella may also be fractured transversely by violent contraction of the quadriceps – for example, in trying to stop a backwards fall. In this case, the tear extends outwards into the quadriceps expansion, allowing the upper bone fragment to be pulled proximally; there may be a gap of over 5 cm (2 in) between the bone ends. Reduction is impossible by closed manipulation and operative repair of the extensor expansion is imperative.

Occasionally, this same mechanism of sudden forcible quadriceps contraction tears the quadriceps expansion above the patella, ruptures the ligamentum patellae or avulses the tibial tubercle.

It is interesting that, following complete excision of the patella for a comminuted fracture, knee function and movement may return to near‐100% efficiency; it is difficult, then, to ascribe any particular function to this bone other than protection of the soft tissues of the knee joint anteriorly.

The tibia (Fig. 164)

The upper end of the tibia is expanded into the medial and lateral condyles, the former having the greater surface area of the two. Between the condyles on the upper surface of the tibia (tibial plateau) is the intercondylar area, which bears, at its waist, the intercondylar eminence, projecting upwards slightly on either side as the medial and lateral intercondylar tubercles.

Anterior aspect of the tibia and fibula of the right side with lines marking the intercondylar eminence, medial condyle, lateral condyle, head of fibula, lateral malleolus, medial malleolus, lateral surface, etc. — **Fig. 164** The tibia and fibula of the right side. (a) Anterior aspect. (b) Posterior aspect.

The tuberosity of the tibia is at the upper end of the anterior border of the shaft and gives attachment to the ligamentum patellae.

The anterior aspect of this tuberosity is subcutaneous, only excepting the infrapatellar bursa immediately in front of it.

The shaft of the tibia is triangular in cross‐section, its anterior border and anteromedial surface being subcutaneous throughout their whole extent. The subcutaneous surface is crossed only by the easily visible great saphenous vein, accompanied by the saphenous nerve, immediately in front of the medial malleolus (Fig. 153).

The posterior surface of the shaft bears a prominent oblique line at its upper end termed the soleal line, which not only marks the tibial origin of the soleus but also delimits an area above, into which is inserted the popliteus.

The lower end of the tibia is expanded and quadrilateral in section, bearing an additional surface, the fibular notch, for the lower tibiofibular joint.

The medial malleolus projects from the medial extremity of the bone and is grooved posteriorly by the tendon of tibialis posterior.

The inferior surface of the lower end of the tibia is smooth, cartilage‐covered and forms, with the malleoli, the upper articular surface of the ankle joint.

The fibula (Fig. 164)

The fibula serves three functions:

It gives origin to several muscles.
It forms part of the ankle (talocrural) joint.
It serves as a pulley for the tendons of peroneus longus and brevis.

From its proximal to distal end the fibula comprises a head with a styloid process (into which is inserted the tendon of biceps), neck (around which passes the common peroneal nerve; Fig. 154), shaft and lateral malleolus. The distal end of the shaft just proximal to the lateral malleolus bears a roughened surface on its medial aspect for the lower tibiofibular joint below which is the articular facet for the talus. A groove on the posterior aspect of the malleolus lodges the tendons of peroneus longus and brevis.

A note on growing ends and nutrient foramina in the long bones

The shaft of every long bone bears one or more nutrient foramina which are obliquely placed; this obliquity is the result of unequal growth at the upper and lower epiphyses. The artery is obviously dragged in the direction of more rapid growth and the direction of slope of entry of the nutrient foramen therefore points away from the more rapid growing end of the bone.

Growth of the long bones of the lower limb takes place principally at the epiphyses at the lower end of the femur and at the upper end of the tibia. This is in contrast to the upper limb where bone growth occurs mainly at the upper end of the humerus and at the lower ends of the radius and ulna.

The direction of growth of the long bones can be remembered by a little jingle, which runs:

‘From the knee, I flee

To the elbow, I grow.’

With one exception, the epiphysis of the growing end of a long bone is the first to appear and last to fuse with its diaphysis; the exception is the epiphysis of the upper end of the fibula which, although at the growing end, appears after the distal epiphysis and fuses after the latter has blended with the shaft.

The site of the growing end is of considerable practical significance; for example, if a child has to undergo an above‐elbow amputation, the humeral upper epiphyseal line continues to grow and the elongating bone may well push its way through the stump end, requiring reamputation.

The bones of the foot

These are best considered as a functional unit and are therefore dealt with together under ‘the arches of the foot’ (see pages 249–251).

The hip joint (Figs 165, 166)

Diagrammatic horizontal section of the right hip viewed from proximal aspect with lines marking the inferior gluteal vessels, gluteus maximus, sciatic nerve, gemellus superior, greater trochanter, etc. — **Fig. 165** (a) The immediate relations of the hip joint (in diagrammatic horizontal section; right hip, viewed from proximal aspect). (b) Scout diagram indicating the level of the section.

Scout diagram of the right hip with a horizontal line indicating the level of the section. — **Fig. 165** (a) The immediate relations of the hip joint (in diagrammatic horizontal section; right hip, viewed from proximal aspect). (b) Scout diagram indicating the level of the section.

Anterior aspect of the right hip with lines marking the external iliac and femoral artery lying on tendon of psoas, inguinal ligament, pubofemoral ligament, illiofemoral (Y-shaped) ligament. — **Fig. 166** The anterior aspect of the right hip. Note that the psoas tendon and the femoral artery are intimate anterior relations of the joint.

The hip joint is the largest joint in the body. To the surgeon, the examiner and, therefore, the student it is also the most important.

It is a perfect example of a ball‐and‐socket joint. Its articular surfaces are the femoral head and the horseshoe‐shaped articular surface of the acetabulum, which is deepened by the fibrocartilaginous labrum acetabulare. The non‐articular lower part of the acetabulum, the acetabular notch, is closed off below by the transverse acetabular ligament. From this notch is given off the ligamentum teres, passing to the fovea on the femoral head.

The capsule of the hip is attached proximally to the margins of the acetabulum and to the transverse acetabular ligament. Distally, it is attached along the trochanteric line, the bases of the greater and lesser trochanters and, posteriorly, to the femoral neck approximately 1.25 cm (0.5 in) from the trochanteric crest. From this distal attachment, capsular fibres are reflected onto the femoral neck as retinacula and provide one pathway for the blood supply to the femoral head (see ‘The femur’, Fig. 159).

Note that acute osteomyelitis of the upper femoral metaphysis will involve the neck, which is intracapsular and which will therefore rapidly produce a secondary pyogenic arthritis of the hip joint.

Three ligaments reinforce the capsule:

the iliofemoral (Y‐shaped ligament of Bigelow) – which arises from the anterior inferior iliac spine, bifurcates, and is inserted at each end of the trochanteric line (Fig. 166);
the pubofemoral – arising from the iliopubic junction to blend with the medial aspect of the capsule;
the ischiofemoral – arising from the ischium to be inserted into the base of the greater trochanter.

Of these, the iliofemoral is by far the strongest and resists hyperextension strains on the hip. In posterior dislocation it usually remains intact.

The synovium of the hip covers the non‐articular surfaces of the joint and occasionally bulges out anteriorly to form a bursa beneath the psoas tendon where this crosses the front of the joint.

Movements

The hip (a ball‐and‐socket joint) is capable of a wide range of movements – flexion, extension, abduction, adduction, medial and lateral rotation and circumduction.

The principal muscles acting on the joint are:

flexors – iliacus and psoas major assisted by rectus femoris, sartorius, pectineus;
extensors – gluteus maximus, the hamstrings;
adductors – adductor longus, brevis and magnus assisted by gracilis and pectineus;
abductors – gluteus medius and minimus, tensor fasciae latae;
lateral rotators – principally gluteus maximus assisted by the obturators, gemelli and quadratus femoris;
medial rotators – tensor fasciae latae and anterior fibres of gluteus medius and minimus. Medial rotation is therefore a much weaker movement than lateral rotation.

The body is an amazingly economical machine. Walk across the room with your hand on one buttock – gluteus maximus does not contract in quiet walking and extension of the hip is carried out entirely by the hamstrings. Now, forcibly extend your hip and feel your gluteus maximus on that side being called into action in vigorous extension of the hip joint.

Relations (Fig. 165)

The hip joint is surrounded by muscles:

anteriorly – iliacus, psoas major and pectineus, together with the femoral artery vein and nerve;
laterally – tensor fasciae latae, gluteus medius and minimus;
posteriorly – the tendons of piriformis, obturator internus with the gemelli, quadratus femoris, the sciatic nerve and, more superficially, gluteus maximus;
superiorly – the reflected head of rectus femoris lying in contact with the joint capsule;
inferiorly – the obturator externus, passing back to be inserted into the trochanteric fossa.

Surgical exposure of the hip joint therefore inevitably involves considerable and deep dissection.

The lateral approach comprises splitting down through the thick fascia behind the tensor fasciae latae, and then through the proximal part of vastus lateralis. On a deeper plane gluteus medius and minimus are incised longitudinally to reach the femoral neck. Further access may be obtained by detaching the greater trochanter with the gluteal insertions.

The anterior approach passes between sartorius medially and tensor fasciae latae laterally, and on a deeper plane, between the rectus femoris medially and the glutei medius and minimus laterally. The reflected head of rectus femoris is then divided to expose the anterior aspect of the hip joint. More room may be obtained by detaching these glutei from the external aspect of the ilium.

The posterior approach is through an angled incision commencing at the posterior superior iliac spine, passing to the greater trochanter and then dropping vertically downwards from this point. Gluteus maximus is split in the line of its fibres and then incised along its tendinous insertion. Deep to gluteus maximus, the short lateral rotators are divided a few centimetres medial to their attachments on the greater trochanter. The medial stumps of the divided short lateral rotators are retracted medially to protect the sciatic nerve. An excellent view of the posterior aspect of the hip joint is thus obtained.

Nerve supply

Hilton’s law states that the nerves crossing a joint supply the muscles acting on it, the skin over the joint and the joint itself. The hip is no exception and receives fibres from the femoral, sciatic and obturator nerves. It is important to note that these nerves also supply the knee joint and, for this reason, it is not uncommon for a patient, particularly a child, to complain bitterly of pain in the knee and for the cause of the mischief, the diseased hip, to be overlooked.

Tags: Clinical Anatomy

Jun 28, 2019 | Posted by admin in ANATOMY | Comments Off

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