1. HANDOUTS FOR PRACTICAL SESSIONS
MODULE AN220.II 2009-2010
PART 2
PRACTICAL SESSIONS 7 AND 8:
“LOWER LIMB OSTEOLOGY, GLUTEAL REGION, PELVIC GIRDLE, LUMBOSACRAL
PLEXUS, MUSCULOSKELETAL ANAT. OF THIGH, KNEE, LEG AND FOOT”
OBJECTIVES:
INTRODUCTION:
Note: In this and subsequent practical sessions please use the atlas provided to locate and
identify different anatomical landmarks and relations. The practicals are mainly directed self-
learning so you will not be “taught” what you need to know and identify, you will accomplish
this by yourself. Contents extracted from Anatomy Notes from UCC by Prof. J.P. Fraher
LOWER LIMB OSTEOLOGY
1. PELVIS
The pelvis is the lower part of the trunk. It has a poorly defined boundary with the abdomen
above it. Its skeleton is a major element of the lower body wall. This forms a bony ring
circumscribing the lower part of the body cavity. It consists of three bones: the median sacrum
dorsally and the two innominate bones laterally and anteriorly.
The sacrum, has been mentioned previously in more detail when studying the vertebral
column, consists of five vertebrae fused together. This has a concave surface facing the pelvic
cavity. It is relatively smooth, but possesses transverse ridges where the intervertebral discs
were previously located, before the sacral vertebrae fused together in development.
The innominate or hip bone consists of three parts, originally three separate bones, but which
fuse together during development: the ilium, the ischium and the pubis.
The ilium forms the upper component and has an extensive, flattened blade for muscle
attachment. Its upper margin includes the iliac crest, which stands out on the lateral body wall
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2. and marks the upper limit of the pelvis. The ischium forms the lower, posterior component. It
has a prominent body, with a heavily developed lower part (the ischial tuberosity0, which
transmits much of the body weight during sitting. The pubis forms the anterior component. This
has a body and two rami [or branches], which are continuous with the ischium.
The three bones come together at the acetabulum [see below]. The ilium articulates with the
sacrum at the sacroiliac joint. This is a synovial joint between two L-shaped [auricular] surfaces,
one on each bone. It has a very strong posterior ligament, which stabilises it. Stability is also
enhanced by the fact that the articular surfaces are somewhat irregular. Being reciprocally
curved, they fit into one another. This is advantageous in weight transmission, preventing the
wedge-shaped sacrum from moving downwards and driving the two innominate bones apart.
The part of the ilium between the sacroiliac joint and the acetabulum is thick and heavy, an
adaptation for weight transmission between the vertebral column and the lower limb,
bilaterally. The two pubic bones are apposed in the midline anteriorly, where the pubic
symphysis, a secondary cartilaginous joint, intervenes between them. There is little movement
between the bones forming the pelvis. What little there is, is enhanced in later pregnancy, and
allows for some adaptation of the pelvis to the foetal
head traversing it.
2.a
Pelvic details
1. Pelvis 2.b 2.i
a. Acetabulum
b. Obturator foramen
2. Ilium 2.f 2.c
a. Iliac crest
b. Iliac fossa
c. Articular surface 2.d
d. Greater sciatic notch 2.f
e. Lesser sciatic notch
f. Anterior superior and inferior iliac spines
3.b
g. Posterior superior iliac spine
h. Anterior, posterior, inferior gluteal lines
1.a
i. Iliac tuberosity
3. Ischium
a. Ischial tuberosity 1.b 4.b
3.a
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3. 2.a
b. Spine of ischium 2.i
c. Ramus of ischium
d. Body 2.b
4. Pubis 2.g
a. Body of pubis
b. Pubic tubercle 2.c
c. Pubic rami
d. Pubic crest
e. Symphyseal surface
eal 2.d
4.a
3.b
4.c 3.d
3
2.e
4.e 4.c 1.b 3.c
3.a
16
2. FEMUR
5
The femur is the thigh bone and is the longest bone in the body. The shaft makes up the
greater part of its length. At its upper end lies the neck. This extends upwards and medially
.
6
at an angle to the shaft and ends above in the head. This makes up approximately
.
two thirds of a sphere. The lower end of the femur takes part in forming the knee
o
joint. This consists of two femoral condyles. Each of these projects distally from the
.
7
lower end of the shaft, one medial and one lateral. They are fused together
anteriorly. Each condyle carries a spiral articular surface for the tibia distally. These
ach
surfaces are continuous anteriorly with the surface for the patella [knee cap] anteriorly, on
the lower end of the shaft. There are two prominent projections for muscle attachment at
its upper end: the trochanters – the greater is lateral and the lesser is below and medial.
8
Features to identify in the femur:15
15 9
1) Head 10 12
2) Neck 15 13
11
3) Greater trochanter
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4. 4) Lesser trochanter
5) Intertrochanteric line and crest
6) Gluteal tuberosity
7) Linea aspera 3
8) Popliteal surface
9) Adductor tubercle
10)Medial epicondyle 2 1
11)Medial condyle 4
12)Lateral epicondyle,
13)Lateral condyle
14)Patellar surface
15)Intercondylar fossa
16)Fovea
14
3. TIBIA
The tibia is the stronger of the two bones in the leg. [The other is the fibula.] The tibia is a long
bone, which has a shaft which is triangular in cross section over much of its length. The sharp
anterior margin is the shin. The upper end of the bone is broadened to form a plateau. This has
.
two articular surfaces, a medial and a lateral, each of which lies on the upper surface of a tibial
condyle. Between the surfaces is the rough intercondylar area. The lower end of the tibia is
.
broadened and a thick, strong projection extends downwards on the medial side of the ankle –
projection
the medial malleolus.
Features to identify:
1. Upper end, lower end
2. Medial condyle
3. Lateral condyle
4. Intercondylar eminence – tubercles
5. Articular facet for fibula
6. Tibial tuberosity
7. Surfaces – Lateral, medial, posterior
8. Borders – Anterior (shin), interosseous, medial
9. Soleal line
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5. 10. Medial malleolus
11. Grooves for flexor hallucis longus, tibilais posterior
12. Fibular notch
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6. 4. FIBULA
The fibula is a long, slender bone, lying lateral to the tibia. It articulates with the tibia below the
level of the knee joint and also at its lower end, where it projects below the tibia to form the
lateral malleolus. It takes only a very minor part in the formation of the knee joint: The lateral
collateral ligament of the knee joint is attached to it.
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7. Features to identify:
1. Head
a. Styloid process
b. Articular facet
2. Neck
3. Borders – anterior, interosseous, posterior
4. Surfaces – medial, lateral, posterior
5. Medial crest
6. Lateral malleolus
7. Malleolar fossa
8. Articular surface of lateral malleolus
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8. 5. HIP JOINT
The hip joint is between the head of the femur and the acetabulum. The fit is deep and so the
hip joint is stable, being rarely dislocated.
The acetabulum is the socket on the innominate bone for the
femur and so forms the superior part of the hip joint. It is
concave and has an articulating surface, which comprises a
crescent-shaped strip of bone [the lunate surface], forming its
superior part. Its lower, central portion is rough and non-
articular, being covered by fat and synovial membrane.
The lunate surface of the acetabulum and almost the entire
surface of the head of the femur are covered with articular
1
cartilage. The free edge of the acetabulum is deepened by a
ring of fibrous cartilage – the labrum of the acetabulum.
The capsule of the
joint is attached to
the two bones a little beyond the margin of the
acetabulum and to the lower end of the femoral neck.
Much of the femoral neck is therefore within the hip
joint cavity. This tends to compromise its blood supply.
If the neck is fractured, the viability of the head of the
femur is threatened because the blood vessels to the
head may be interrupted. If this is cut off, the head may die – avascular necrosis [necrosis =
death] – if the supply through the delicate ligament of the head of the femur (1) is inadequate.
The capsule is strengthened by three major ligaments - the iliofemoral (2), ischiofemoral(3)
and pubofemoral (4), from the corresponding part of the innominate bone to the femoral neck
and the bone just distal to it. The first of these is particularly strong and protects the joint
against over-extension.
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9. Anterior View: Posterior View:
2
4 3
2
The hip joint has three degrees of freedom of movement. It possesses flexion and extension in
the parasagittal plane, abduction and adduction in the coronal plane, and rotation can take
place around longitudinal axes.
Flexion is produced by the iliopsoas muscle and the rectus femoris part of the quadriceps
femoris muscle;
Extension is produced by the gluteus maximus and hamstring muscles;
Adduction is produced by the adductor muscles;
Abduction is produced by the gluteus medius and minimus, as well as the tensor fasciae latae.
Abduction is important is setting up the conditions for other movements, particularly flexion
and extension. Because the two feet are on the ground while standing, the pelvis must tilt up to
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10. lift the lower limb and therefore the foot off the ground to facilitate the forward swing in
walking. Accordingly, the abductors on the left side are active in enabling the forward swing of
the right lower limb.
Despite being stable, the hip joint may be dislocated when strong forces are exerted in
particular directions. This frequently happens in car accidents. The force may be great enough
to fracture the head of the femur, a factor in causing osteoarthritis. The acetabulum may not
develop to be as deep as normal, when congenital dislocation of the hip may result. The
articular cartilage on the surfaces is initially over 0.5cm thick, but is eroded during life and so
becomes progressively thinner with time. The result of this ageing process is osteoarthritis,
when the underlying bone is exposed and this is associated with pain.
6. KNEE JOINT
The articular surfaces on the tibial condyles articulate with the corresponding surfaces on the
two condyles of the femur. Each is covered by a layer of articular cartilage. The capsule
connects the bones all around the perimeter of the joint. This is complicated in several ways,
however: For example, the broad tendon of the quadriceps femoris fuses with it superiorly.
Also, there is an opening in it posteriorly through which the tendon of the popliteus muscle
emerges from the point cavity. This arises within the joint from the lateral femoral condyle and
is attached to the upper end of the tibia. [For its function, see below.]
The degree of congruity between the femur and tibia is low. The concave tibial surfaces are
much less curved than the spiral surfaces of the femur. Accordingly, the knee joint has complex
mechanisms for stabilisation. It has several strong ligaments:
Being a hinge joint, it has two collateral ligaments, one on its medial and one on its lateral side.
These prevent abduction and adduction, respectively.
Within the joint are two cruciate ligaments, connecting the bones, lying in approximately
parasagittal planes and crossing one another. These are attached to the intercondylar area of
the tibia and to the femoral condyles. They bind the bones together, forcing them towards one
another in the several positions which the joint may adopt.
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11. Congruity of the articulating Posterior View
surfaces is enhanced by the
presence of two menisci. Each of
.
these projects into the joint cavity
from the capsule around most of
its perimeter. They are attached at
their anterior and posterior ends
to the tibia. They have the
advantage of being flexible and of
adapting their form to the varying
[spiral] outline of the femoral
condyles. Because of this spiral
profile, the congruity of the knee
joint surfaces varies considerably at differing stages of flexion – extension.
Anterior View
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12. The patella glides up and down on the groove on the patellar surface on the lower end of the
femoral shaft. Both surfaces are covered with hyaline cartilage. The lower end of the patella is
connected to the tibial tuberosity on the anterior surface of the upper end of the shaft, by the
patellar tendon. This is the true insertion of the quadriceps femoris. This muscle is attached to
the upper end of the patella, which is therefore a sesamoid bone in its tendon.
The knee joint has two degrees of freedom of movement. The principal movements are flexion
and extension. It also undergoes rotation – thus the tibia can be rotated voluntarily on the
femur - especially evident when the joint is flexed through 90º. During walking, towards the
end of extension of the femur on the tibia, the femur rotates medially, thus locking the joint by
bringing it into the close packed position. On commencing the next stage of the walking cycle,
the joint is unlocked – by the action of the popliteus muscle.
Muscles producing extension: the powerful quadriceps [femoris]; sartorius, especially when
combined flexion of hip and knee take place;
flexion: the hamstrings: biceps femoris, semimembranosus, semitendinosus.
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13. The collateral ligaments may be injured in impacts on the joint from the sides, such as from
automobiles; or in accidents such as skiing injuries which entail powerful laterally or medially
directed forces acting on the joint.
MUSCLES AND MOVEMENTS OF THE LOWER LIMB
Unlike that of the upper limb, the lower limb girdle is part of the body wall. Thus, the bone of
the proximal segment of the lower limb, the femur, articulates directly with the trunk skeleton.
MUSCLES AND MOVEMENTS OF THE THIGH
1) Anterior Muscles
a) Sartorius
This long strap muscle runs from the anterior superior iliac spine to the upper part of the
medial surface of the tibia. It runs in front of the hip joint and behind the axis of the knee joint,
therefore it flexes both hip and knee. It is supplied by the femoral nerve.
b) Quadriceps Femoris
This composite muscle consists of four parts. Of these, the most anterior, the rectus femoris,
arises from the hip bone and passes in front of the hip joint. The other three parts of the
muscle, the vastus lateralis, the vastus medialis and the vastus intermedius arise from the
posterolateral, posteromedial and anterior aspects of the shaft of the femur, respectively. All
four are inserted into the upper, anterior part of the shaft of the tibia through a common
tendon, and thence to the patella. The patella is in turn attached to the tibia through the
ligamentum patellae. The patella is therefore a sesamoid bone in the quadriceps tendon. The
quadriceps is supplied by the femoral nerve. All four parts of the muscle extend the knee.
Since the rectus, in addition, passes in front of the hip joint, it flexes this joint.
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14. c) Ilipsoas
This composite muscle is in two parts; the psoas major and the iliacus. The psoas arises from
the lumbar part of the vertebral column. It runs caudally and laterally along the brim of the
lesser pelvis. Here it is joined on its lateral side by the fibres of the iliacus coming from the iliac
fossa. The composite muscle then runs into the thigh behind the inguinal ligament. It is
attached to the lesser trochanter of the femur. The composite muscle flexes the hip joint.
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15. Acting from their lower attachments, both iliopsoas muscles bend the lumbar part of the
vertebral column forwards (as in sitting
up from the supine position). The
psoas, acting on its own, flexes the
lumbar spine laterally. The lumbar
plexus lies in the substance of the
psoas major. It supplies this muscle as
well as the iliacus.
2) Muscles of the Buttock
a) Gluteus Maximus
This powerful muscle arises from the
dorsal aspects of the sacrum,
sacrotuberous ligament and ilium. Its
fibres run downwards and laterally. It
is inserted into the gluteal tuberosity
of the femur. It is also inserted beyond
this into the tibia and the head of the
fibula via the iliotibial tract of the
fascia lata, a very thick and powerful
sheet of deep fascia. It is supplied by the inferior gluteal nerve from the sacral plexus. It
extends and laterally rotates the thigh at the hip joint. Thus, it swings the lower limb
backwards when the foot is off the ground. When the foot is on the ground it extends the
trunk on the lower limb, as in standing up from the sitting position or in climbing stairs. It is
also important in stabilising the knee joint.
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16. b) Tensor Fasciae Latae
This muscle arises from the iliac crest and is inserted into the iliotibial tract. It is supplied by the
superior gluteal nerve. It abducts the
hip joint and stabilises the knee joint.
c) Gluteus Medius and Minimus
These muscles lie deep to the gluteus
maximus. They arise from the ilium.
They run laterally above the hip joint to
be attached to the greater trochanter of
the femur. They are supplied by the
superior gluteal nerve. Both abduct the
hip. They are especially important in
walking. While the more mobile limb is
raised from the ground and is being
swung forwards, the gluteus medius and
minimus on the opposite side are active,
thus preventing the pelvis from sagging
on the side of the unsupported mobile
limb. If they are paralysed it sags:
Trendelenburg’s sign.
d) Small Muscles
Like the shoulder joint, the hip joint
possesses a cuff of short muscles
surrounding it, running from the pelvis to the femur. These function primarily as ligaments of
variable length and tension, stabilising the hip during the powerful movements brought about
by the much stronger muscles crossing the joint.
These include:
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17. 1. Piriformis runs laterally behind the hip joint from the sacrum to the greater trochanter.
It is supplied from the sacral plexus.
2. Obturator Externus and Internus come from the outer and inner surfaces, respectively,
of the obturator membrane. The internus runs backwards to emerge from the pelvis through
the lesser sciatic foramen and run laterally behind the joint. The externus spirals backwards
and laterally around the neck of the femur. Both are attached to the greater trochanter. The
externus is supplied by the obturator nerve, the internus from the sacral plexus.
3. The rectangular Quadratus Femoris muscle runs laterally behind the hip joint from the
ischial tuberosity to the upper part of the shaft of the femur. It is supplied from the sacral
plexus.
e) Adductor Group
The adductor muscles run from the pubis and ischium downwards and laterally to the linea
aspera on the back of the shaft of the femur. There are three main adductors. Their nerve of
supply is the obturator.
1. The adductor magnus is the largest of the group. It is attached to the whole length of
the linea aspera and the medial supracondylar line. It separates the anterior from the posterior
compartments of the thigh. The part which arises most posteriorly (i.e. from the ischial
tuberosity) is morphologically part of the hamstring (extensor) muscle group. The lower
attachment of this part is to the medial femoral condyle. The adductor magnus is supplied by
two nerves: the adductor part by the obturator, the hamstring part by the sciatic. The femoral
artery passes backwards from the anterior compartment of the thigh into the popliteal fossa by
passing through an opening bounded by the femur and the two parts of the adductor magnus.
2. The Adductor Brevis arises from the pubis and is attached to the upper part of the linea
aspera. It lies immediately in front of the adductor magnus.
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18. 3. The Adductor Longus arises from the pubis and is attached to the linea aspera behind
and somewhat lower down than the brevis. All three adductors flex the femur from the
extended position and also adduct it. They are therefore very important in kicking movements.
4. The Gracilis runs from the pubis to the upper part of the medial surface of the tibia.
Supplied by the obturator nerve, it adducts the thigh, flexes the knee joint and, especially when
the knee is flexed, rotates the tibia medially on the femur.
5. The Pectineus is a small muscle and arises from the superior ramus of the pubis. It
passes downwards to the shaft of the femur behind the lesser trochanter. It is usually supplied
by the femoral nerve. It adducts and flexes the femur.
The femoral sheath and canal
The femoral sheath is a tapering cone of fascia which extends along the femoral vessels. It is
continuous with the fasciae lining the abdominal wall (transversalis and iliolumbar fasciae).
Traced distally, it tapers and blends with the perivascular tissue surrounding the femoral
vessels. The fascial cone is larger than the vessels so that a redundant space is left medial to
them. This is the femoral canal, which is about 2 cm long. Its proximal opening, the femoral
ring, is bounded medially by the lacunar ligament, anteriorly by the inguinal ligament,
posteriorly by the pectineus muscle and laterally by the femoral vein. The femoral canal
contains loose connective tissue and, commonly, a lymph node.
Femoral Hernia
In femoral hernia, the hernial sac protrudes down through the femoral canal, then forwards
through the relatively weak cribriform fascia which closes the semilunar hiatus in the upper
anteromedial part of the fascia lata. It then projects forwards below and lateral to the pubic
tubercle. This helps to distinguish it from inguinal herniae. However, as it enlarges further it
tends to project upwards and medially towards the pubic tubercle.
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19. Femoral herniae are commoner in females than in males because females have relatively large
femoral canals, due to greater breadth of the pelvis and the smaller size of the femoral vessels.
Femoral herniae tend to become obstructed and to strangulate more readily than inguinal
because of the smallness and relative rigidity of the femoral ring.
The Femoral Triangle and Adductor Canal
The femoral triangle is bounded laterally by the sartorius, above by the inguinal ligament and
medially by the medial border of the adductor longus. On the muscles of the femoral triangle
lie the femoral artery, vein and nerve. The femoral artery leaves the lower part of the triangle
through the adductor canal. This canal is bounded anterolaterally by the vastus medialis,
posteromedially by the adductor longus and magnus and anteriorly by the sartorius. The artery
then leaves the front of the thigh and the adductor canal by passing backwards through the
opening in the adductor magnus. Once it has passed through this opening it is called the
popliteal artery.
f) Hamstring Group
Each of the three hamstring muscles is attached above to the ischial tuberosity, runs distally
along the back of the thigh and passes behind the knee joint to be attached to one of the bones
of the leg. The lateral hamstring is the biceps femoris. This muscle has an additional head
arising from the back of the femur. It is attached to the head of the fibula. The two remaining
hamstrings lie medially. Of these, the semitendinosus is superficial and the semimembranosus
is deep. Both are attached to the tibia, the semitendinosus is superficial and
semimembranosus deep. Both are attached to the tibia, the semimembranosus to the back of
the medial tibial condyle, the semitendinosus to the upper medial part of the shaft close to the
attachments of sartorius and gracilis. All three hamstrings are supplied by the sciatic nerve.
Since all three cross both hip and knee joints posteriorly, they have a combined action; they
extend the hip and flex the knee. (The femoral head of the biceps acts only on the knee). Using
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20. the lower attachments as the origin, the hamstrings extend the trunk on the femur, as in
straightening up from the bent position. They also rotate the leg at the knee especially when
the joint is flexed. The biceps rotates it laterally, the other two rotate it medially.
MUSCLES AND MOVEMENTS OF THE LEG AND FOOT
The muscles of the leg lie in three compartments – anterior, posterior and peroneal (lateral).
Muscles of the Anterior Compartment
Each of these muscles passes distally into the dorsum of the foot by passing deep to the
extensor retinacula. The upper extensor retinaculum runs from the tibia to the fibula just
above the ankle, the lower from the calcaneus to the medial malleolus and the fascia on the
medial side of the foot. As they pass deep to these retinacula, the tendons are contained in
synovial sheaths. Each of these muscles is supplied by the deep peroneal nerve.
1. The Tibialis Anterior arises from the upper part of the tibia and is inserted into the
medial cuneiform and first metatarsal bones. It dorsiflexes the ankle joint and inverts the foot.
2. The Extensor Digitorum Longus arises from the fibula. It divides into four tendons, one
to each of the lateral four toes. The attachment of these is exactly similar to that of the
corresponding muscle is the hand (q.v.). This muscle dorsiflexes the ankle and extends the
lateral four toes at the metatarsophalangeal joints.
3. The Extensor Hallucis Longus arises deep to the previous two, from the fibula. It is
inserted into the dorsal surface of the distal phalanx of the great toe. It dorsiflexes the ankle
and extends the great toe. Acting from below, all of the three above muscles prevent the body
from overbalancing backwards at the ankle joint.
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21. 4.
Peroneal Muscles
The peroneus longus and brevis arise from the lateral aspect of the fibula. They run distally
behind the lateral malleolus, being bound down by retinacula attached to the lateral malleolus
and the lateral side of the calcaneus. The brevis is attached to the base of the fifth metatarsal.
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22. The longus hooks medially around the
cuboid bone and runs across the plantar
surface of the foot to be inserted into the
medial cuneiform and first metatarsal
bones. Both muscles lie in a synovial
sheath as they pass behind the lateral
malleolus. The longus lies in a synovial
sheath as it crosses the sole of the foot.
Where it bends around the cuboid, it
contains a sesamoid fibrocartilage or bone.
Both peronei are supplied by the superficial
peroneal nerve. Both evert the foot and
help to prevent medial overbalancing. They
help to maintain the arched form of the
foot.
Muscles of the Posterior Compartment
1. Gastrocnemius. Each of the two bellies of the gastrocnemius arises from the posterior
part of the corresponding condyle of the femur and from the capsule of the knee joint. Both
are attached through a common tendon, the tendo calcaneus, to the posterior surface of the
calcaneus. The gastrocnemius is supplied by the tibial nerve. It flexes the knee joint and
powerfully plantarflexes the ankle. It is of major importance in providing propelling force in
walking and running. In fracture of the shaft of the femur it pulls the lower fragment
backwards out of alignment with the upper fragment.
2. The Soleus arises from the upper parts of the tibia and fibula and from a tendinous arch
between the bones. It is attached to the deep surface of the tendo calcaneus. It is supplied by
the tibial nerve. It plantar flexes the ankle joint. The soleus mainly functions as a postural
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23. muscle, preventing the body from falling forwards at the ankle during upright standing. (A
vertical line through the centre of gravity of the body passes in front of the ankle joint).
3. The Popliteus arises from the lateral surface of the lateral femoral condyle within the
knee joint capsule. Its fibres emerge from the joint to be inserted into the upper part of the
dorsal surface of the tibia. It is supplied by the tibial nerve. It rotates the femur laterally on the
tibia when the foot is on the ground. When the knee is fully extended and bearing weight, the
femur is in a position of medial rotation on the tibia, the joint being locked and close-packed. In
the first stage of flexion, the popliteus undoes the rotation of the femur by laterally rotating it
on the tibia.
4. The Flexor Digitorum Longus lies deep to the soleus. It arises from the tibia. Its tendon
enters the foot by passing behind the medial malleolus. It then divides into four digitations
which are inserted into the distal phalanges of each of the four lateral toes, in a manner exactly
similar to those of the flexor digitorum profundus in the hand. The four digitations run
obliquely distally and laterally through the foot. When the muscle contracts, the line of pull,
which would be oblique, is rendered longitudinal by the action of a short muscle of the foot.
This is the flexor accessorius which run from the calcaneus to each of the digitations of the long
muscle, so as to make its line of pull parallel to the long axis of the foot. The longus is supplied
from the tibial nerve. It flexes all the joints of the lateral four toes, helping them to grip the
ground firmly. It also plantar flexes the ankle. Acting from below it prevents forward
overbalancing.
5. The Flexor Hallucis Longus also lies deep to the soleus. It arises from the fibula. It enters
the foot behind the medial malleolus and is inserted into the plantar surface of the distal
phalanx of the great toe. It is supplied by the tibial nerve. It flexes all the joints of the great toe
and also the ankle joint.
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24. 6. The Tibialis Posterior is the deepest muscle of the leg. It arises from the tibia, the fibula
and the interosseous membrane between them. Its tendon enters the foot behind the medial
malleolus. It is inserted into most of the tarsal bones. It is supplied by the tibial nerve. It
plantar flexes the ankle joint and inverts the foot. Acting from its lower attachment, it prevents
lateral overbalancing.
The tendons of the three previous muscles are each surrounded by a synovial sheath and pass
through an osseofibrous tunnel as they enter the foot. This tunnel lies deep to the flexor
retinaculum which runs between the medial malleolus and the calcaneus.
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25. 100

26. Intrinsic Muscles of the Foot
The Extensor Digitorum Brevis muscle forms the fleshy mass on the dorsum of the foot. It
arises from the calcaneus. It has four digitations, each of which fuses with a tendon of the long
extensor of the medial four toes. It is supplied by the deep peroneal nerve.
The remaining intrinsic muscles lie on the plantar aspect of the foot. Their main importance lies
in their mass action during walking; fine control of individual toes is of little importance, though
it can be learned. A further important function of the intrinsic muscles is to support the arches
of the foot. In this function, they aid the ligaments, the plantar aponeurosis and the long
muscles which run on the undersurface of the skeleton. Those intrinsic muscles of the foot
which lie on its plantar aspect are arranged in four layers.
First Layer (superficial or plantar)
1. The Abductor Hallucis runs from the calcaneus to the base of the proximal phalanx of the
great toe, which it helps to flex at the metatarsophalangeal joint.
2. The Flexor Digitorum Brevis corresponds to the flexor digitorum superficialis in the upper
limb. It arises from the plantar aspect of the calcaneus. It gives rise to four tendons, through
which the tendons of the flexor digitorum longus pass. Each of its tendons is attached to the
middle phalanx of one of the lateral four toes. It flexes the proximal interphalangeal and
metatarsophalangeal joints.
3. The Abductor Digiti Minimi runs from the calcaneus to the proximal phalanx of the little
toe. It helps to flex the metatarsophalangeal joint.
Second Layer
1. The Flexor Accessorius (see above)
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27. 2. The four Lumbrical muscles correspond to those in the hand.
Third Layer
This consists of three muscles, the short flexors of the great and little toes, and the adductor of
the great toe. Each of these arises from the plantar aspect of the tarsus and/or metatarsus.
Each is inserted into the proximal phalanx of the appropriate toe. The movement brought
about by each is that indicated by its name.
Fourth Layer (deepest)
This consists of the Interossei, which are similar to the corresponding muscles in the hand in
their attachments and actions. However, the imaginary line in relation to which they move the
toes passes through the second toe. Thus the longitudinal axis of the foot differs from that of
the hand in that it passes through the second, not the third, digit.
Nerve supply
All of the intrinsic muscles on the plantar aspect of the foot are supplied by the lateral plantar
nerve, except the following: abductor hallucis, flexor hallucis brevis, flexor digitorum brevis and
the first (most medial) lumbrical. These are supplied by the medial plantar nerve.
NERVES OF THE LOWER LIMB
Lumbosacral Plexus
The lumbosacral plexus is made up by ventral rami. It supplies the muscles of the lower limb.
The upper lumbar nerves also supply part of the trunk and the lower sacral and coccygeal
nerves also supply the perineum. The plexus is derived from the five lumbar, five sacral and
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28. first coccygeal nerves. The lumbar plexus lies in the substance of the psoas major muscle and
the branches emerge from this. The sacral plexus lies on the dorsal wall of the pelvis.
Each of the ventral rami contributing to the plexuses receives a grey ramus communicans from
the sympathetic chain. Through these, autonomic fibres are distributed to the tissues of the
lower limb. Each of the first two lumbar ventral rami sends a white ramus communicans to the
sympathetic trunk. The ventral rami of S2 and 3 send fine branches to the autonomic plexuses
in the pelvis. These are preganglionic parasympathetic fibres which are concerned in the
innervation of the pelvic viscera and part of the colon.
Lumbar Plexus
1. Iliohypogastric and Ilioinguinal nerves run laterally anterior to the quadratus lumborum
and pierce the transversus abdominis to run forwards in the abdominal wall between this
muscle and the internal oblique. They give cutaneous supply to a strip of skin running above
the inguinal ligament, the upper medial part of the thigh, the scrotum and the penis or labium
majus.
2. The Genitofemoral nerve emerges onto the anterior surface of the psoas, descends along
it and supplies the scrotum or labium majus and the upper medial part of the thigh.
3. The Lateral Cutaneous Nerve of Thigh runs laterally on the iliacus and enters the thigh by
passing behind the lateral part of the inguinal ligament. It supplies the skin on the lateral
aspect of the thigh.
4. The Obturator Nerve is the nerve to the adductor group of muscles. It emerges from the
medial border of the psoas, runs forwards along the lateral wall of the lesser pelvis and enters
the thigh through the obturator canal. Here it divides into two branches, anterior and
posterior, which run downwards in planes anterior and posterior to the adductor brevis. In
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29. addition to supplying the adductor longus, brevis and part of the adductor magnus, the it
supplies the obturator externus and the gracilis. It is sensory to both hip and knee joints.
This supply to both joints may result in referred pain from hip disease being misdirected to the
knee, giving the patient a false impression of knee disease. The opposite can also occur.
5. The Femoral Nerve supplies the muscles of the front of the thigh, the pectineus, the
sartorius and the quadriceps. It also supplies sensory branches to the hip and knee joints and
to the skin on the anteromedial surface of the lower limb as far as the medial side of the foot.
It emerges from the lateral aspect of the psoas major and runs into the thigh in the grove
between the psoas and iliacus.
Its sensory branches supply the area of skin already mentioned. One of these, the saphenous
nerve, runs downwards through the femoral triangle and adductor canal with the femoral
vessels. It becomes superficial in the leg by emerging between the sartorius and gracilis. It
then descends on the medial side of the leg where it accompanies the great saphenous vein.
This nerve supplies the skin on the front and medial side of the leg and on part of the medial
aspect of the foot.
6. Motor branches from the plexus supply the psoas and iliacus muscles.
7. The lumbosacral trunk consists of part of L4 together with L5. The former emerges from the
medial aspect of the psoas major and joins the latter. The combined trunk descends into the
pelvis to join the sacral plexus.
Sacral Plexus
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30. The ventral rami contributing to the plexus converge to form a large fan-shaped band. This
descends on the posterior pelvic wall to emerge from the pelvis into the back of the thigh
through the greater sciatic foramen, below the piriformis, as the sciatic nerve.
A large number of small nerves arise from the plexus and supply the muscles of the perineum,
together with those around the hip joint. Thus they supply the obturator internus, the
piriformis and the quadratus femoris.
The gluteal nerves, superior and inferior, leave the pelvis above and below the piriformis
respectively. They enter the gluteal region to supply the three gluteal muscles and the tensor
fasciae latae.
Branches from the plexus supply the coccygeus and levator ani muscles.
1. The pudendal nerve is the principal nerve of the perineum. It leaves the pelvis through
the lower part of the greater sciatic foramen, descends on the superficial aspect of the
sacrospinous ligament and runs forwards into the perineum, together with its accompanying
vessels. It runs forwards on the obturator internus muscle, above the level of the ischiopubic
rami. Here is lies in the pudendal canal which is bounded by fascia. In this position it may be
readily anaesthetised, a procedure termed pudendal block, which is frequently performed
during childbirth. Through its inferior rectal branch, the pudendal nerve supplies the sphincter
ani externus, part of the levator ani, the skin of the anal canal and that surrounding the anus.
Other branches of the pudendal nerve supply the muscles of the urogenital triangle of the
perineum, the skin of the scrotum or labium majus, the skin of the penis or clitoris and the
erectile tissue of both male and female external genitals.
2. The posterior cutaneous nerve of the thigh arises from the sacral plexus, leaves with the
sciatic nerve and descends along the back of the thigh and popliteal fossa. It runs down to
supply the skin over the back of the thigh, the popliteal fossa and the upper half of the back of
the leg. It also supplies the skin of the perineum and the lower part of the buttock.
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31. 3. The Sciatic Nerve is the largest nerve in the body. It consists of a medial tibial nerve and a
lateral common peroneal nerve bound together. It enters the thigh from under the lower
border of the piriformis. It runs downwards on the posterior surface of the short muscles of the
hip joint and then on the adductor magnus. It lies deep to the gluteus maximus and the
hamstrings. In the thigh, it supplies the latter group of muscles and ends by dividing into tibial
and common peroneal branches. This division is usually at the uppermost part of the popliteal
fossa, but may occur at a much higher level.
4. The Common Peroneal Nerve nerve is distributed to the skin of the anterolateral surface
of the leg and of the dorsum of the foot, as well as to the muscles of the anterior and peroneal
compartments of the leg and the extensor digitorum brevis.
It also gives sensory supply to the knee, ankle and foot joints. It runs downwards and laterally
under the biceps femoris as far as the head of the fibula. It divides into deep and superficial
peroneal nerves as it winds round the lateral surface of the neck of the fibula under cover of
the peroneus longus. As it lies on the neck of the fibula, it can be rolled against the bone. In
this situation it is vulnerable to injury. The deep peroneal nerve runs downwards and medially
on the fibula under the extensor digitorum longus to reach the interosseous membrane. Here
it is joined by the anterior tibial artery and veins.
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