site logo

The Surgical Dissection Of The Popliteal Space And The Posterior Crural Region

Sources: Surgical Anatomy

On comparing the bend of the knee with the bend of the elbow, as evident

a correspondence can be discerned between these two regions, as exists

between the groin and the axilla.

Behind the knee-joint, the muscles which connect the leg with the thigh

enclose the space named popliteal. When the integuments and subcutaneous

substance are removed from this place, the dense fascia lata may be seen

binding thes
muscles so closely together as to leave but a very narrow

interval between them at the mesial line. On removing this fascia, B B M

M, Plate 65, the muscles part asunder, and the popliteal space as

usually described is thereby formed. This region now presents of a

lozenge-shaped form, B J D K, of which the widest diameter, D J, is

opposite the knee-joint. The flexor muscles, C D J, in diverging from

each other as they pass down from the sides of the thigh to those of the

upper part of the leg, form the upper angle of this space; whilst its

lower angle is described by the two heads of the gastrocnemius muscle, E

E, arising inside the flexors, from the condyles of the femur. The

popliteal space is filled with adipose substance, in which are embedded

several lymphatic bodies and through which pass the principal vessels

and nerves to the leg.

In the dissection of the popliteal space, the more important parts first

met with are the branches of the great sciatic nerve. In the upper angle

of the space, this nerve will be found dividing into the peronaeal, I,

and posterior tibial branches, H K. The peronaeal nerve descends close

to the inner margin of the tendon, J, of the biceps muscle; and, having

reached the outer side of the knee, I*, Plate 66, below the insertion of

the tendon into the head of the fibula, winds round the neck of this

bone under cover of the peronaeus longus muscle, S, to join the anterior

tibial artery. The posterior tibial nerve, H K, Plate 65, descends the

popliteal space midway to the cleft between the heads of the

gastrocnemius; and, after passing beneath this muscle, to gain the inner

side of the vessels, H*, Plate 66, it then accompanies the posterior

tibial artery. On the same plane with and close to the posterior tibial

nerve in the popliteal space, will be seen the terminal branch of the

lesser sciatic nerve, together with a small artery and vein destined for

distribution to the skin and other superficial parts on the back of the

knee. Opposite the heads of the gastrocnemius, the peronaeal and

posterior tibial nerves give off each a branch, both of which descend

along the mesial line of the calf, and joining near the upper end of the

tendo Achillis, the single nerve here, N, Plate 65, becomes superficial

to the fascia, and thence descends behind the outer ankle to gain the

external border of the foot, where it divides into cutaneous branches

and others to be distributed to the three or four outer toes. In company

with this nerve will be seen the posterior saphena vein, L, which,

commencing behind the outer ankle, ascends the mesial line of the calf

to join the popliteal vein, G, in the cleft between the heads of the


On removing next the adipose substance and lymphatic glands, we expose

the popliteal vein and artery. The relative position of these vessels

and the posterior tibial nerve, may now be seen. Between the heads of

the gastrocnemius, the nerve, H, giving off large branches to this

muscle, lies upon the popliteal vein, G, where this is joined by the

posterior saphena vein. Beneath the veins lies the popliteal artery, F.

On tracing the vessels and nerve from this point upwards through the

popliteal space, we find the nerve occupying a comparatively superficial

position at the mesial line, while the vessels are directed upwards,

forwards, and inwards, passing deeply, as they become covered by the

inner flexor muscles, C D, to the place where they perforate the tendon

of the adductor magnus on the inner side of the lower third of the


The popliteal artery, F, Plate 66, being the continuation of the

femoral, extends from the opening in the great adductor tendon at the

junction of the middle and lower third of the thigh, to the point where

it divides, in the upper, and back part of the leg, at the lower border

of the popliteus muscle, L, into the anterior and posterior tibial

branches. In order to expose the vessel through this extent, we have to

divide and reflect the heads of the gastrocnemius muscle, E E, and to

retract the inner flexors. The popliteal artery will now be seen lying

obliquely over the middle of the back of the joint. It is deeply placed

in its whole course. Its upper and lower thirds are covered by large

muscles; whilst the fascia and a quantity of adipose tissue overlies its

middle. The upper part of the artery rests upon the femur, its middle

part upon the posterior ligament of the joint, and its lower part upon

the popliteus muscle. The popliteal vein, G; adheres to the artery in

its whole course, being situated on its outer side above, and posterior

to it below. The vein is not unfrequently found to be double; one vein

lying to either side of the artery, and both having branches of

communication with each other, which cross behind the artery. In some

instances the posterior saphena vein, instead of joining the popliteal

vein, ascends superficially to terminate in some of the large veins of

the thigh. Numerous lymphatic vessels accompany the superficial and deep

veins into the popliteal space, where they join the lymphatic bodies,

which here lie in the course of the artery.

The branches derived from the popliteal artery are the muscular and the

articular. The former spring from the vessel opposite those parts of the

several muscles which lie in contact with it; the latter are generally

five in number--two superior, two inferior, and one median. The two

superior articular branches arise from either side of the artery, and

pass, the one beneath the outer, the other beneath the inner flexors,

above the knee-joint; and the two inferior pass off from it, the one

internally, the other externally, beneath the heads of the gastrocnemius

below the joint; while the middle articular enters the joint through the

posterior ligament. The two superior and inferior articular branches

anastomose freely around the knee behind, laterally, and in front, where

they are joined by the terminal branches of the anastomotic, from the

femoral, and by those of the recurrent, from the anterior tibial. The

main vessel, having arrived at the lower border of the popliteus muscle,

divides into two branches, of which one passes through the interosseous

ligament to become the anterior tibial; while the other, after

descending a short way between the bones of the leg, separates into the

peronaeal and posterior tibial arteries. In some rare instances the

popliteal artery is found to divide above the popliteus muscle into the

anterior, or the posterior tibial, or the peronaeal.

The two large muscles, (gastrocnemius and soleus,) forming the calf of

the leg, have to be removed together with the deep fascia in order to

expose the posterior tibial, and peronaeal vessels and nerves. The

fascia forms a sheath for the vessels, and binds them close to the deep

layer of muscles in their whole course down the back of the leg. The

point at which the main artery, F, Plate 66, gives off the anterior

tibial, is at the lower border of the popliteus muscle, on a level with

N, the neck of the fibula; that at which the artery again subdivides

into the peronaeal, P, and posterior tibial branches, O, is in the

mesial line of the leg, and generally on a level with the junction of

its upper and middle thirds. From this place the two arteries diverge in

their descent; the peronaeal being directed along the inner border of

the fibula towards the back of the outer ankle; while the posterior

tibial, approaching the inner side of the tibia, courses towards the

back of the inner ankle. The gastrocnemius and soleus muscles overlie

both arteries in their upper two thirds; but as these muscles taper

towards the mesial line where they end in the tendo Achillis, V V, Plate

65, they leave the posterior tibial artery, O, with its accompanying

nerve and vein, uncovered in the lower part of the leg, except by the

skin and the superficial and deep layers of fasciae. The peronaeal

artery is deeply situated in its whole course. Soon after its origin, it

passes under cover of the flexor longus pollicis, R, a muscle of large

size arising from the lower three fourths of the fibula, N, and will be

found overlapped by this muscle on the outer border of the tendo

Achillis, as low down as the outer ankle. The two arteries are

accompanied by venae comites, which, with the short saphena vein, form

the popliteal vein. The posterior tibial artery is closely followed by

the posterior tibial nerve. In the popliteal space, this nerve crosses

to the inner side of the posterior tibial artery, where both are about

to pass under the gastrocnemius muscle, to which they give large

branches. Near the middle of the leg, the nerve recrosses the artery to

its outer side and in this relative position both descend to a point

about midway between the inner ankle and calcaneum, where they appear

having the tendons of the tibialis posticus and flexor longus digitorum

to their inner side and the tendon of the flexor longus pollicis on

their outer side. Numerous branches are given off from the nerve and

artery to the neighbouring parts in their course.

The varieties of the posterior crural arteries are these--the tibial

vessel, in some instances, is larger than usual, while the peronaeal is

small, or absent; and, in others, the peronaeal supplies the place of

the posterior tibial, when the latter is diminished in size. The

peronaeal has been known to take the position of the posterior tibial in

the lower part of the leg, and to supply the plantar arteries. In

whatever condition the two vessels may be found, there will always be

seen ramifying around the ankle-joint, articular branches, which

anastomose freely with each other and with those of the anterior tibial.

The popliteal artery is unfavourably circumstanced for the application

of a ligature. It is very deeply situated, and the vein adheres closely

to its posterior surface. Numerous branches (articular and muscular)

arise from it at short intervals; and these, besides being a source of

disturbance to a ligature, are liable to be injured in the operation, in

which case the collateral circulation cannot be maintained after the

main vessel is tied. There is a danger, too, of injuring the middle

branch of the sciatic nerve, in the incisions required to reach the

artery; and, lastly, there is a possibility of this vessel dividing

higher up than usual. Considering these facts in reference to those

cases in which it might be supposed necessary to tie the popliteal

artery--such cases, for example, as aneurism of either of the crural

arteries, or secondary haemorrhages occurring after amputations of the

leg at a time when the healing process was far advanced and the bleeding

vessels inaccessible,--it becomes a question whether it would not be

preferable to tie the femoral, rather than the popliteal artery. But

when the popliteal artery itself becomes affected with aneurism, and

when, in addition to the anatomical circumstances which forbid the

application of a ligature to this vessel, we consider those which are

pathological,--such as the coats of the artery being here diseased, the

relative position of the neighbouring parts being disturbed by the

tumour, and the large irregular wound which would be required to isolate

the disease, at the risk of danger to the health from profuse

suppuration, to the limb from destruction of the collateral branches, or

to the joint from cicatrization, rendering it permanently bent,--we must

acknowledge at once the necessity for tying the femoral part of the main


When the popliteal artery happens to be divided in a wound, it will be

required to expose its bleeding orifices, and tie both these in the

wound. For this purpose, the following operation usually recommended for

reaching the vessel may be necessary. The skin and fascia lata are to be

incised in a direction corresponding to that of the vessel. The extent

of the incision must be considerable, (about three inches,) so as the

more conveniently to expose the artery in its deep situation. On laying

bare the outer margin of the semi-membranosus muscle, while the knee is

straight, it now becomes necessary to flex the joint, in order that this

muscle may admit of being pressed inwards from over the vessel. The

external margin of the wound, including the middle branch of the sciatic

nerve, should be retracted outwards, so as to ensure the safety of that

nerve, while room is gained for making the deeper incisions. The adipose

substance, which is here generally abundant, should now be divided,

between the mesial line and the semimembranosus, till the sheath of

the vessels be exposed. The sheath should be incised at its inner side,

to avoid wounding the popliteal vein. The pulsation of the artery will

now indicate its exact position. As the vein adheres firmly to the coats

of the artery, some care is required to separate the two vessels, so as

to pass the ligature around each end of the artery from without inwards,

while excluding the vein. While this operation is being performed in a

case of wound of the popliteal artery, the haemorrhage may be arrested

by compressing the femoral vessel, either against the femur or the os


In the operation for tying the posterior tibial artery near its middle,

an incision of three or four inches in extent is to be made through the

skin and fascia, in a line corresponding with the inner posterior margin

of the tibia and the great muscles of the calf. The long saphena vein

should be here avoided. The origins of the gastrocnemius and soleus

muscles require to be detached from the tibia, and then the knee is to

be flexed and the foot extended, so as to allow these muscles to be

retracted from the plane of the vessels. This being done, the deep

fascia which covers the artery and its accompanying nerve is next to be

divided. The artery will now appear pulsating at a situation an inch

from the edge of the tibia. While the ligature is being passed around

the artery, due care should be taken to exclude the venae comites and

the nerve.