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COMPARTMENTS OF THE LEG
The leg is divided into 
anterior, lateral and
posterior fascial
compartments separated
by the tibial interosseous
membrane and anterior
and posterior inter
muscular septa ,which
pass inwards from the
investing deep fascia of
the leg.
COMPARTMENTS OF THE LEG
These fascial 
compartments are
inextensible.
Any swelling within these
compartments as a result
of bleeding , infection or
venous obstruction
produces a rise in the
intra compartmental
pressure that will hinder
its blood supply and
produce tender ,swollen

CUTANEOUS NERVES
(1) Antero- 
lateral surface of
the leg
A. The upper part
Lateral 
cutaneous nerve
of the calf.
B. The lower part
Superficial 
peroneal nerve


CUTANEOUS NERVES
Both from Common 
Peroneal nerve
(2) Anteromedial surface
of the leg : from
Saphenous nerve
(from Femoral) nerve. 
MUSCLES
1. Tibialis Anterior. 
2. Extensor Digitorum
longus.
3. Extensor Hallucis 
longus.
4. Peroneus Tertius. 

ORIGIN
Only Tibialis Anterior is
attached to the tibia.
The others are attached to
the fibula.
Only one 
extensor(peroneus
tertius) is confined to the
foot.


TIBIALIS ANTERIOR
Origin : 
upper ½ of lateral 
surface of tibia and
interosseous
membrane.
TIBIALIS ANTERIOR
Insertion : 
Medial cuneiform bone 
and the base of the
adjacent (1st ) metatarsal
bone.
Action : 
(1) Dorsiflexion of the 
foot.
(2) Inversion of the foot.
(3) Maintains the medial
long. arch.

EXTENSOR DIGITORUMLONGUS
Origin : 
upper 2/3 of 
anterior surface of
fibula and
interosseous
membrane.
Extensor Digitorum Longus
Insertion 
The four tendons pass to 
the lateral four toes where
they form the extensor
expansion.
EXTENSOR EXPANSION
The central part of the 
expansion is inserted to
the bases of the middle
phalanges of the lateral
four toes.
The two lateral slips 
are inserted in the bases
of the distal phalanges
of the same toes.
Extensor Digitorum Longus
Action 
Extension of the 
lateral four toes. +
weak Dorsiflexion.
During walking 
these muscles pull
the leg forward
over the ground.
EXTENSOR HALLUCIS LONGUS
Origin : 
middle ½ of the 
anterior surface of
the fibula and the
interosseous
membrane.
Extensor Hallucis longus
Insertion 
Base of the distal 
phalanx of the big toe.
Action 
(1) Extension of the big 
toe.
(2) Extension of the foot 
(Dorsiflexion).
(3) Inversion of the foot. 
PERONUS TERTIUS
Origin :
lower 1/3 of the
anterior surface of
the fibula and the
interosseous
membrane.
Peroneus Tertius
Insertion 
Medial side of the 
dorsal surface of
the 5th metatarsal
bone.
Action: 
(1) Extension of 
the foot.
2) Eversion of the 
foot.
NERVE SUPPLY
All the muscles are 
supplied by the Deep
Peroneal (Anterior
Tibial nerve).
ANTERIOR TIBIAL ARTERY
Origin : 
It arises as a 
terminal branch of
the popliteal artery
at the lower border
of popliteus.
COURSE
It passes forward above
the interosseous
membrane and it enters
the anterior
compartment through
an opening in the upper
part of the membrane.
In company with the 
deep peroneal nerve.

COURSE
In the upper part of its 
course it lies deep to the
muscles while in the lower
part it lies superficial in
front of the lower end of the
tibia.
COURSE
Here its pulsations can
easily be felt.
It has the tendon of the
extensor hallucis longus
on its medial side and
the deep peroneal nerve
and the tendons of
extensor digitorum
longus on its lateral side.


TERMINATION
In front of the ankle 
joint , it becomes the
Dorsalis Pedis
artery.
BRANCHES
1. Muscular. 
2. Anastomotic :
Malleolar around
the ankle.
Recurrent around
the knee.



DEEP PERONEAL NERVE
(ANTERIOR TIBIAL 
NERVE)
Origin : 
It is one of the two 
terminal branches of the
common peroneal nerve.
It arises at the lateral 
side of the neck of the
fibula in the substance of
peroneus longus.

COURSE
It passes around the 
neck of the fibula into
the anterior
compartment and
descends in company
with the anterior tibial
vessels in front of the
interosseous membrane.

COURSE
Upper 1/3 : 
It is lateral to the 
anterior tibial vessels.
Middle third 
It is superficial ( 
anterior ) to the
anterior tibial vessels.
Lower 1/3 
It is lateral to the 
anterior tibial vessels.

COURSE
It passes under the 
extensor retinacula
and enters the dorsum
of the foot where it
divides into terminal
medial and lateral
branches.
TERMINAL BRANCHES
Medial branch 
supplies the skin of
the adjacent sides
of the 1st and 2nd
toes.
Lateral branch 
supplies the
extensor digitorum
brevis.
BRANCHES
(1) Muscular to : 
Dorsiflexors (anterior 
compartment of the leg).
(2) Cutaneous : 
The skin in the web of 
the first toe.
(3) Articular : 
to the ankle joint. 
DORSUM OF THE FOOT
1. Nerves: Cutaneous 
2. Artery : Dorsalis 
Pedis
3. Veins : Dorsal 
Venous arch.
4. Muscle : Extensor 
Digitorum Brevis
CUTANEOUS NERVES
(1) Saphenous 
nerve
It passes in front 
of the medial
malleolus.
It supplies the skin
along the medial
side of the foot as
far as the head of
the 1st metatarsal
bone.

CUTANEOUS NERVES
(2) SUPERFICIAL 
PERONEAL
It supplies: 
1. The dorsum of 
the foot.
2. The medial side 
of the big toe.
3.The adjacent 
sides of the 2nd ,3rd
,4th ,5th toes.
CUTANEOUS NERVES
(3) DEEP PERONEAL 
It supplies: 
Adjacent sides of the 
first and second toes.
(6) SURAL nerve 
It supplies: 
lateral side of the 
foot and little toe.
CUTANEOUS NERVES
The nail beds and
the skin over the
dorsal surfaces of
the terminal
phalanges is
supplied by the
Medial and
Lateral plantar
nerves.

DORSALIS PEDIS ARTERY
It is the major source of 
arterial supply to the foot.
Course : 
It begins mid way between
the malleoli and runs deep
to the inferior retinaculum
between the extensor
hallucis longus and the
extensor digitorum
longus on the dorsum of
the foot.


COURSE
It is crossed by the 
inferior extensor
retinaculum and the 1st
tendon of extensor
digitorum brevis.
Lateral to it : terminal 
part of deep peroneal
nerve and tendon of
extensor digitorum longus.
Medial to it : tendon of 
extensor hallucis longus.
PULSE
The pulse of dorsalis 
pedis artery is easily felt
as it passes between the
tendons of extensor
hallucis longus and
extensor digitorum 
longus , midway
between the medial and
lateral malleoli.
(the foot is slightly 
dorsiflexed)
PULSE
A diminished or 
absent pulse usually
suggests vascular
insufficiency
resulting from
arterial disease.
BRANCHES
1. Lateral tarsal. 
2. Arcuate : 
It runs under the 
extensor tendons
to the bases of the
metatarsal bones .
It gives metatarsal
branches.
3. 1ST dorsal 
metatarsal.
TERMINAL BRANCHES
It passes to the 1st 
interosseous space
where it divides into :
A. Deep plantar artery
It passes to the sole of
the foot where it joins
the lateral plantar
artery and completes the
plantar arch.
B. 1st dorsal 
metatarsal artery.

DORSAL VENOUS ARCH
It lies in the 
subcutaneous tissue
over the heads of the
metatarsal bones.
It drains on the medial
side into the Great
Saphenous vein.
On the lateral side to 
the Small Saphenous
vein.

EXTENSOR DIGITORUM BREVIS
Origin : 
from the anterior 
surface of the
calcaneum and the
inferior retinaculum.
It is divided into four 
tendons to the medial
four toes.
The most medial one is
the (Extensor Hallucis
Brevis).

EXTENSOR DIGITORUM BREVIS
Insertion : 
Extensor hallucis 
brevis to the base of
the proximal phalanx
of the big toe.
The other three pass to
the 2nd,3rd and 4th toes
with the other extensor
tendons (of the
extensor expansion).

EXTENSOR DIGITORUM BREVIS
Nerve supply : 
deep peroneal 
nerve.
Action : 
It extends the 2nd ,
3rd and 4th toes at
the inter
phalangeal and
metatarso phalangeal joints.

LATERAL COMPARTMENT
(1) Peroneal 
muscles : Longus
& Brevis. They are
important in
maintaining
balance during
standing.
(2) Nerves : 
Superficial
Peroneal nerve.
(3) Arteries : 
Peroneal artery.
ORIGIN
Peroneus Longus :
upper 2/3 of the
lateral surface of the
fibula.
Peroneus Brevis :
lower 2/3 of the
lateral surface of the
fibula.
INSERTION
Peroneus Longus :
Base of the 1st metatarsal
bone.
Medial cuneiform bone.
It passes in a groove under
the cuboid bone.
Peroneus Brevis :
The tendon passes behind and
directly in contact with the
lateral malleolus to be
inserted to
Tuberosity of the base of the
5th metatarsal bone.
ACTION
Peroneus Longus :
(1) Plantar flexion of the
foot
(2) Eversion of the foot.
(3) Holding up the lateral
longtudinal arch.
(4) A tie to the transverse
arch.
ACTION
Peroneus Brevis :
(1) Plantar flexion of the
foot.
(2) Eversion of the foot.
(3) Holding up the lateral
longitudinal arch.
Forced inversion (twisted
ankles) often result in
avulsion of the base of the
5th metatarsal.
NERVE SUPPLY
Superficial
Peroneal
(Musculocutaneouss
nerve).

SUPERFICIAL PERONEAL
NERVE
Origin : 
It is one of the terminal 
branches of the common
peroneal nerve.
It arises in the substance of
peroneus longus lateral to the
neck of the fibula.
COURSE
It descends between
peroneus longus and
brevis muscles.
In the lower part of the
leg it emerges through
the deep fascia and
divides into medial
and lateral branches.

BRANCHES
(1) Muscular to: 
peroneus longus and
brevis.
BRANCHES
(2) Cutaneous 
to:
A. The lower part 
of the front of the
leg.
B. The dorsum of 
the foot.
C. The skin of the 
dorsal surface of
all the toes
BRANCHES
Except : 
1. The adjacent 
sides of the first
and second toes.
2. The lateral side
of the little toe.

PERONEAL ARTERY
Origin : 
From the posterior 
tibial artery in the
posterior compartment.
Branches : 
perforating branches 
to the Inferior part of
the lateral
compartment.
SUPERIOR PART
The muscles are supplied
by perforating branches
from the anterior tibial
artery.
