D. J. (Daniel John) Cunningham.

Cunningham's manual of practical anatomy (Volume 1) online

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easily done in the living than the dead body. The nerve
should be followed to the back of the head of the fibula
where it can be pressed against the proximal part of the
soleus muscle. When the knee joint is extended the
rounded tendon of the adductor magnus can be felt, as
it passes to its insertion into the adductor tubercle, which lies
on the upper border of the medial condyle at the distal end
of the medial supracondylar ridge. The adductor tubercle
is an important practical landmark, for it indicates the plane
of junction of the body of the femur with the distal epiphysis.

In muscular subjects the two heads of the gastrocnemius
muscle form prominent rounded cushions which extend from
the distal part of the popliteal area into the proximal part of
the posterior region of the leg.

Proximal to the popliteal region the posterior region of the
thigh presents a smooth rounded surface, on which, in thin

VOL. I 20



306 THE INFERIOR EXTREMITY

subjects, indications of the outlines of the bellies of the
hamstring muscles may be seen.

Dissection. Reflection of the Skin. Place a block under
the knee to support the limb and to render tense the muscles
which form the boundaries of the popliteal fossa. Incisions
(i) A vertical incision along the median line of the limb from
the junction of the middle and distal thirds of the thigh to the
junction of the proximal fourth with the distal three-fourths
of the leg. (2) A transverse incision at the proximal end of
the vertical incision. (3) A transverse incision at the distal
end of the vertical incision. Each of the two transverse
incisions should extend halfway round the limb.

The two flaps of skin defined by the incisions (21 and 22,
Fig. 126) must be separated from the superficial fascia and turned
to their respective sides.

Superficial Fascia Vena Saphena Parva (O.T. External
Saphenous Vein) Branches of the Posterior Cutaneous
Nerve of the Thigh (O.T. Small Sciatic). When the skin
is reflected the fatty layer of the superficial fascia of the
popliteal region is brought into view. It presents no peculiar
features, and, as a rule, it contains only a moderate amount
of fat, amidst which the following structures must be sought :
(i) The proximal part of the small saphenous vein-, (2) the
terminal part of the posterior cutaneous nerve of the thigh ;

(3) branches of the posterior cutaneous nerve of the thigh ;

(4) the posterior branch of the medial cutaneous nerve of
the thigh ; (5) the anastomotic peroneal nerve.

Dissection. Look first for the small saphenous vein. It
ascends along the middle line of the back of the calf and pierces
the deep fascia over the distal part of the popliteal fossa. As
the proximal part of the vein is being cleaned secure the terminal
part of the posterior cutaneous nerve of the thigh which runs
alongside of the vein. At a higher level, in the fat in the middle
line of the proximal part of the popliteal area one or more twigs
from the posterior cutaneous nerve of the thigh may be found,
piercing the deep fascia on their way to the skin.

When the medial side of the thigh was dissected the posterior
branch of the medial cutaneous nerve of the thigh was found
descending along the posterior border of the sartorius muscle
(Fig 127). It should be followed now as it descends behind the
medial boundary of the popliteal fossa to the back of the calf.
The peroneal anastomotic nerve may be found at the lower and
lateral part of the popliteal area as it pierces the deep fascia
covering the lateral head of the gastrocnemius muscle (Fig. 127).
In some cases, however, the nerve pierces the deep fascia at a
much more distal level. In such cases it will not be found until
the back of the leg is dissected. After the small saphenous
vein and the nerves* mentioned have been secured and cleaned,
remove the remains of the superficial fascia, but be careful to
avoid injury to the deep fascia which is somewhat thin.



POPLITEAL FOSSA 307

Fascia Poplitea (Popliteal Fascia). Although it is thin,
the deep fascia of the popliteal region possesses considerable
strength owing to the transverse fibres which are interwoven
amidst its longitudinal fibres. As the dissector removes the
fascia he will notice that it is firmly attached on each side to
the tendons of the muscles which bound the fossa poplitea.
Proximally, it is continuous with the fascia lata of the thigh.

Before the popliteal fascia is interfered with the dissector is recom-
mended to read the following two paragraphs, which deal in a general way
with the boundaries and contents of the popliteal fossa.

Boundaries. The popliteal fossa is diamond - shaped.
Proximally and laterally it is bounded by the biceps femoris
muscle ; whilst proximally and medially are the semitendinosus
and the semimembranosus muscles^ the former lying upon the
posterior surface of the latter. On the medial side of the
knee, anterior to the semimembranosus, lie the gracilis, the
sartorius, and the tendon of the adductor magnus. The
fossa is bounded, distally, by the converging heads of
the gastrocnemius. In the formation of the distal and lateral
boundary the lateral head of the gastrocnemius is assisted
by the small plantaris muscle.

Contents of the Fossa. The principal objects within the
popliteal fossa are the tibial and common peroneal nerves and
the popliteal artery and vein, with their branches and
tributaries, but the most superficial structure, in the proximal
part of the space, is the posterior cutaneous nerve of the thigh,
which runs along the middle line, immediately subjacent to
the popliteal fascia, until it pierces that fascia in the distal
part of the space. Separated from the posterior cutaneous
nerve of the thigh by a thin layer of fat is the large tibial
nerve. It lies superficial to the popliteal vein and artery
which are situated in a much deeper plane in close contact
with one another. The common peroneal nerve lies along
the upper lateral boundary of the fossa, under cover of the
posterior margin of the biceps femoris. Both the tibial and
the common peroneal nerves give off branches of which the
majority are easily found, but their articular twigs are delicate
and are easily destroyed by the dissector who does not
exercise sufficient care. One of the articular nerves,
however, is derived neither from the tibial nor the common
peroneal nerve, but from the deep division of the obturator



308



THE INFERIOR EXTREMITY



nerve previously dissected (p. 273). It descends in close
apposition to the popliteal artery. Other important contents
of the fossa are lymph-glands, some of which lie relatively
superficial, near the point where the small saphenous vein



M. biceps femoris



Common peroneal nerve
(O.T. ext. popliteal)



A. genu superior lateralis

Common trunk of lateral

cutaneous nerve of the

calf and anastomotic

peroneal nerve

Plantaris



M. gastrocnemius
lateral head



Medial cutaneous nerve

of the calf

(O.T. ramus com-

municans tibialis)




M. semitendinosus

M. fsemimembranosus
Tendon of adductor magnus

Popliteal artery

Tibial nerve (int. popliteal)

A. genu superior medialis

Cut end of small
saphenous vein
Medial condyle of femur
Tendon of semitendinosus
M. gastrocnemius, medial head
- Tendon of gracilis
. Popliteal vein

Nerve to popliteus muscle

Tendon of plantaris muscle
Nerve to soleus

Soleus



FIG. 132. Dissection of the Left Popliteal Fossa. The proximal boundaries
have been pulled apart and the aponeurosis into which the two heads of
the gastrocnemius is attached has been split and the heads have been
displaced to their respective sides.

pierces the popliteal fascia, but the majority are deeply
placed adjacent to the popliteal vein and artery.

Dissection. Do not attempt to open up the popliteal fossa
and display its contents until its proximal boundaries have been
cleaned and their relationships to the fossa have been defined.



POPLITEAL FOSSA 309

The distal boundaries will be cleaned and displayed as some of
the contents of the fossa are secured and followed towards their
terminations.

Clean first the proximal lateral boundary. Make an incision
through the deep fascia along its medial margin, turn the fascia
laterally and expose the biceps femoris. Clean the muscle and its
tendon, follow the tendon to its insertion into the head of the
fibula, and note that at the level of the knee the biceps femoris
crosses the lateral head of the gastrocnemius. After the distal part
of the biceps femoris has been cleaned, turn to the proximal medial
border of the space ; make an incision through the deep fascia
along its lateral margin, and reflect the fascia covering it towards
the medial side to expose the semitendinosus and semimem-
branosus muscle; follow the tendon of the more superficial
semitendinosus muscle to the level of the medial condyle
of the tibia. Then pull the semitendinosus aside and clean the
distal part of the semimembranosus, and follow its tendon
to its insertion into the medial condyle of the tibia. Pre-
serve if possible the muscular branches of the popliteal artery
which enter the lateral part of the muscle, and note that the
tendon of insertion springs mainly from the lateral border and
anterior (deep) surface of the muscle. Pull the part of the
muscle which lies at the level of the medial condyle of the femur
towards the medial side of the knee and display the semi-
membranosus bursa, which lies between the semimembranosus
and the medial head of the gastrocnemius as they cross one
another. The semimembranosus bursa often communicates,
round the medial border of the gastrocnemius, with a bursa
which lies between the medial head of the gastrocnemius and
the back of the knee joint, and that, in turn, communicates with
the cavity of the knee joint. Open the bursa and, if possible,
display the communications which have been mentioned with
the aid of a probe. Now pull the semitendinosus and semi-
membranosus laterally and clean the gracilis, which lies medial
and anterior to them. At the anterior border of the gracilis
the saphenous nerve emerges between the gracilis and the
posterior border of the sartorius accompanied by the saphenous
branch of the arteria genu suprema ; secure the artery and
nerve and follow them downwards to the medial border of the
tibia and note that they accompany the great saphenous vein,
which was exposed when the medial side of the thigh was
dissected. Then pull the gracilis medially and clean the distal
part of the adductor magnus which lies lateral to it.

When the proximal boundaries of the fossa have been cleaned
and examined, seize the posterior cutaneous nerve of the thigh
at the point where it pierces the popliteal fascia (see p. 306), and
follow it to the proximal angle of the fossa, dividing the popliteal
fascia which lies superficial to it ; then remove the remains of
the popliteal fascia from the proximal part of the popliteal area.
Now pull the posterior cutaneous nerve aside, with a hook, and
cut through the fat in the proximal apex of the fossa till the
large tibial nerve is exposed. Follow the tibial nerve distally,
cleaning it, partly with the aid of the handle of the scalpel and
partly by occasional touches with the point of the scalpel, and
secure its cutaneous, muscular, and articular branches. Its
cutaneous branch, the medial cutaneous nerve of the calf, arises



3 io THE INFERIOR EXTREMITY

from its posterior aspect and descends between the two heads
of the gastrocnemius. Follow that branch to the distal angle
of the fossa, dividing the popliteal fascia superficial to it. The
articular branches are three in number, superior medial genicular,
inferior medial genicular, and middle genicular. All three
branches spring from the medial side of the tibial nerve, the
superior branch at or above the proximal angle of the fossa, and
the other two at more distal levels. Each joins a corresponding
branch of the popliteal artery, and is distributed with it. The
superior branch leaves the fossa above the medial condyle of
the femur, the inferior branch turns medially below the medial
condyle of the tibia, and the middle branch pierces the posterior
ligament of the knee joint. The muscular branches arise about
the middle of the fossa and pass to the two heads of the gastro-
cnemius, the plantaris, the soleus, and the popliteus ; the heads
of the gastrocnemius must be separated to obtain a proper view
of these branches. The branch to the soleus will be recognised
because it passes between the plantaris and the lateral head of
the gastrocnemius. The nerve to the popliteus lies deeply in
the angle between the heads of the gastrocnemius superficial
to the popliteal artery. It will be followed to its termination
in a subsequent dissection (see p. 403).

When the tibial nerve and its branches have been cleaned
return to the proximal angle of the fossa, dissect in the fat lateral
to the tibial nerve at the medial border of the biceps, and secure
the common peroneal nerve. It descends along the medial
border of the biceps, and leaves the fossa at the lateral angle,
crossing superficial to the plantaris and the lateral head of the
gastrocnemius (Fig. 132). Follow the nerve carefully from
above downwards. Whilst it is in the fossa it gives off two
articular branches, superior lateral genicular, and inferior
lateral genicular, and a cutaneous branch, the anastomolic
peroneal nerve, which crosses the lateral head of the gastro-
cnemius. As the common peroneal nerve lies superficial to
the lateral head of the gastrocnemius it gives off the lateral
cutaneous nerve of the calf; then it passes posterior to the head of
the fibula, from which it is separated by the highest fibres of
the soleus, and disappears between the peroneus longus and the
neck of the fibula. The superior lateral articular branch leaves
the fossa proximal to the lateral condyle of the femur with the
corresponding branch of the popliteal artery. The inferior
lateral articular branch joins the inferior lateral genicular
branch of the popliteal artery at the lateral side of the knee
between the head of the fibula and the lateral condyle of the
femur. The lateral cutaneous nerve of the calf and the anasto-
motic peroneal cutaneous branch sometimes arise from the
common peroneal nerve by a common stem (see Fig. 132).
When the nerves mentioned have been found and cleaned, clean
the two heads of the gastrocnemius and separate the plantaris
from the medial border of the lateral head, taking care not to
injure the nerve to the soleus which passes between the plantaris
and the lateral head of the gastrocnemius. As the muscles are
cleaned, note the branches of the popliteal artery which pass to
them, but divide those branches if they interfere with the separa-
tion of the muscles.

The popliteal vein and its tributaries and the popliteal artery



POPLITEAL FOSSA 311

and its branches must now be cleaned. Pull the tibial nerve
laterally and clear away the fat on the lateral side of the semi-
membranosus at the proximal part of the fossa. The artery
enters the fossa a little distal to the proximal angle, on the medial
side, where it lies close to the floor or anterior boundary of the
fossa. It leaves the fossa at the distal angle at the distal border
of the popliteus muscle. In the proximal part of the fossa the
vein is lateral to the artery. In the middle part of the fossa
it is posterior to the artery, and in the distal part it is medial
to the artery, always intervening between the artery and the tibial
nerve. In the angle between the artery and the vein, in the
proximal part of the fossa, look for the slender genicular branch
of the obturator nerve, and, having secured it, follow it to the point
where it pierces the posterior ligament of the knee joint with
the middle genicular artery. Then proceed to clean the popliteal
artery and its branches and the popliteal vein. Not uncommonly
in addition to the main vein, whose position has been described,
there are two or more accessory venous channels which com-
municate with the main vein and anastomose with one another
round the artery ; if they are present clear them away, but take
care, whilst doing so, not to injure the branches of the artery.
The branches of the artery to the hamstring muscles and the
muscles of the calf are numerous, and, if they interfere with
the cleaning of the main structures, they must be divided, but
the articular branches must be carefully preserved ; they are
five in number, the superior and inferior medial genicular
arteries, the superior and inferior lateral genicular arteries, and
the middle genicular artery. They all lie close to the floor of
the space and are liable to be injured as the soft fat around the
popliteal artery is cleared away. The superior genicular branches
lie at the level of the proximal borders of the condyles of the
femur. They run transversely and they leave the space, the
medial by piercing the posterior intermuscular septum of the
thigh, and the lateral by piercing the lateral intermuscular
septum. The inferior lateral genicular artery also runs trans-
versely, at the level of the interval between the lateral condyle of
the femur and the head of the fibula, but the inferior medial
genicular branch descends obliquely, deep to the medial head of
the gastrocnemius, and then turns forwards, distal to the medial
condyle of the tibia. The middle genicular artery accompanies the
genicular branch of the obturator nerve through the middle part
of the posterior ligament of the knee joint. The final step of
the dissection is the cleaning of the fat from the floor of the
fossa. With the handle of the scalpel scrape the fat away from
the posterior surface of the femur, the posterior ligament of the
knee joint, and the posterior surface of the fascia covering the
popliteus, taking care not to injure the genicular arteries.

Floor of the Fossa. The floor is formed proximo-distally
by (i) the popliteal surface of the femur; (2) the oblique
popliteal ligament of the knee joint ; and (3) by the strong
fascia which covers the popliteus muscle.

The Fossa Poplitea as seen in a Section through the Frozen Knee.

The diamond -shaped space on the back of the knee joint which is brought



3i2 THE INFERIOR EXTREMITY

into view by dissection differs widely from the condition which is observed
when transverse sections are made through this part of the frozen limb
(Fig. 133). Before the integuments and fasciae are removed all the parts
are tightly braced together, and the fossa poplitea is represented merely by
a small intermuscular interval between the distal parts of the hamstring
muscles. The fossa in this condition is rather under an inch wide at its
broadest part. The popliteal artery, therefore, as it traverses the space,
is covered by muscles throughout its whole course, with the exception of a
very small part immediately proximal to the knee joint.

Nervus Cutaneus Femoris Posterior (O.T. Small Sciatic).
The posterior cutaneous nerve of the thigh enters the popliteal
fossa at its proximal angle, and passes distally, immediately
subjacent to the deep fascia. It gives one or two twigs
through the fascia to the skin, and finally pierces the fascia in
the distal part of the fossa. Its terminal twigs are distributed
to the skin over the proximal part of the calf of the leg.

Nervus Tibialis (O.T. Internal Popliteal Nerve). The tibial
nerve enters the fossa at its proximal angle, emerging from
under cover of the biceps femoris. It runs vertically down-
wards to the distal angle and thus bisects the fossa
longitudinally. It commences about the middle of the thigh
as the larger of the two terminal branches of the sciatic
nerve, and it leaves the fossa at the lower border of the
popliteus muscle, and enters the posterior region of the leg.
Its superficial position in the fossa has already been referred
to. When it enters the fossa it lies on the lateral side of the
popliteal vessels, at the mid-length of the space it crosses
superficial to them, and in the distal part of the space it is
medial to them ; consequently the muscular branches given off,
in the lower part of the fossa, to the lateral head of the
gastrocnemius, the plantaris, the soleus, and the popliteus
pass posterior to the vessels on their way to the muscles they
supply.

The branches of the nerve in the popliteal fossa are
classified as cutaneous, muscular, and articular.

The medial cutaneous nerve of the calf is the cutaneous
branch. It arises about the middle of the fossa, and pro-
ceeds distally in the furrow between the two heads of the
gastrocnemius. It will afterwards be seen to unite with the
peroneal anastomotic nerve, a little distal to the middle of the
calf of the leg, to form the nervus suralis (Fig. 127).

The muscular branches supply both heads of the gastro-
cnemius, the plantaris, the soleus, and the popliteus : they
come off in the distal part of the fossa. The branch to the



POPLITEAL FOSSA



popliteus requires special notice. It arises more distally than
the others, and crosses the superficial surface of the popliteal
artery to reach the lateral side of that vessel. It then runs
distally on the posterior surface of the popliteus muscle, and
gains the anterior surface by winding round the distal border.
This will be better seen when the popliteus muscle is dissected.
The articular branches are three in number. They are
given off by the tibial nerve in the proximal part of the fossa,
sometimes even proximal to the fossa, and they accompany
the middle genicular artery and the two medial genicular



Prepatellar bursa



B. Biceps

femoris

G.E. Lateral head
of gastro-
cnemius.

G.I. Medial head
of gastro-
cnemius.
S. Sartorius.
S.M. Semimem-

branosus.
V. Vastus

medialis




semitendinosus



Synovial
cavity of
knee joint



Popliteal artery



Popliteal vein

Tibial nerve (O.T.
int. popliteal)

Common peroneal
nerve (O.T. ext.
popliteal)



FIG. 133. Transverse section through the Popliteal Fossa of the Right
Inferior Extremity.



arteries. That which accompanies the inferior medial artery
is larger than the other two, and can, as a rule, be easily
discovered as it runs along the proximal border of the popliteus
muscle.

Nervus Peronseus Communis (O.T. External Popliteal).
The common peroneal nerve is the smaller of the two terminal
branches of the sciatic nerve. It arises, from the sciatic
nerve, about the middle of the length of the thigh, and it
terminates at the lateral side of the neck of the fibula, under
cover of the peroneus longus, by dividing into a superficial
and a deep peroneal terminal branch. It does not traverse
the entire length of the popliteal fossa, for, as it runs distally



3 J 4



THE INFERIOR EXTREMITY



and laterally along the medial border of the biceps femoris,
it leaves the fossa at its lateral angle, where it crosses the
plantaris and the lateral head of the gastrocnemius ; then it
passes behind the head of the fibula, from which it is



M. semitendinosus

M. semimembranosus

M. biceps femoris



Tibial nerve (O.T.
int. popliteal)

Origin of the peroneal
anastomotic nerve



M. plantaris



Common peroneal

nerve (O.T.

ext. popliteal)



Soleus

Lateral head of

gastrocnemius

(cut across)

Medial cutaneous

nerve of the calf

(O.T. ramus com-

municans tibialis)




| Superficial fascia
Deep fascia

M. gracilis
_ M. sartorius

Superior medial
"genicular artery

-Popliteal vessels

Bursa between
capsule of knee and
'tendon of semi-
membranosus

M. semimembranosus

_ Oblique popliteal
ligament

Inferior medial
genicular artery

M. semitendinosus
(tendon of)

.Great saphenous vein
M. popliteus

Medial head of
M. gastrocnemius
(cut across)



Deep fascia



~~ Small saphenous
vein



FIG. 134. Popliteal Fossa. The two heads of the gastrocnemius and portions
of the semimembranosus and semitendinosus have been removed so as to
display more fully the contents of the fossa.

separated by the upper part of the soleus ; finally it turns
forwards, to its termination, between the lateral side of the
neck of the fibula and the proximal part of the origin of
the peroneus longus. It gives off two cutaneous and three
articular branches.

The cutaneous branches are two in number, viz., the anasto-



PLATE XXI



Femur



A. genu
suprema



Superior
lateral geni-
cular artery



Popliteal
artery



Lateral con-
dyle of femur



Inferior
medial geni-
cular artery



;



Patella



. Medial con- 1
dyle of femur



Muscular
branches



Online LibraryD. J. (Daniel John) CunninghamCunningham's manual of practical anatomy (Volume 1) → online text (page 31 of 44)