The anterior leg compartment contains four muscles - Tibialis Anterior, Extensor Digitorum Longus, Extensor Hallucis Longus, and Peroneus Tertius. These muscles dorsiflex the ankle and extend the toes, arising from the tibia and fibula and inserting at various points on the foot. They are all supplied by the deep peroneal nerve. Injury to this nerve causes foot drop.

1. The Anterior Leg

2. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint

3. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles

4. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles
Extensor Digitorum Longus
Extensor Hallucis Longus
Also extend the toes

5. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles
Extensor Digitorum Longus
Extensor Hallucis Longus
Tibialis Anterior
Also extend the toes

6. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles
Extensor Digitorum Longus
Extensor Hallucis Longus
Tibialis Anterior – also inverts the foot
Also extend the toes

7. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles
Extensor Digitorum Longus
Extensor Hallucis Longus
Tibialis Anterior – also inverts the foot
Peroneus Tertius
Also extend the toes

8. The anterior compartment of the leg contains extensor
muscles that dorsiflex the ankle joint
There are four muscles
Extensor Digitorum Longus
Extensor Hallucis Longus
Tibialis Anterior – also inverts the foot
Peroneus Tertius – also known as Fibularis Tertius
Also extend the toes

9. Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L

10. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L

11. Septum
Septum
Interosseous
Membrane
Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L

12. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment

13. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment

14. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Superficial Posterior
Compartment

15. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Superficial Posterior
Compartment

16. Tibi
a
Fibula
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Anterior Compartment
Superficial Posterior
Compartment

17. Deep Posterior
Compartment
Tibi
a
Fibula
Tibialis Anterior
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Superficial Posterior
Compartment

18. Deep Posterior
Compartment
Tibi
a
Fibula
Tibialis AnteriorTibialis Anterior
ExtensorExtensor
HallucisHallucis
LongusLongus
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Superficial Posterior
Compartment

19. Deep Posterior
Compartment
Tibi
a
Fibula
Tibialis AnteriorTibialis Anterior
ExtensorExtensor
HallucisHallucis
LongusLongus
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
ExtensorExtensor
DigitorumDigitorum
LongusLongus
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Superficial Posterior
Compartment

20. Deep Posterior
Compartment
Tibi
a
Fibula
Tibialis AnteriorTibialis Anterior
ExtensorExtensor
HallucisHallucis
LongusLongus
Cross Section through middle of right leg looking up from foot
anterioranterior
posteriorposterior
ExtensorExtensor
DigitorumDigitorum
LongusLongus
L
A
T
E
R
A
L
M
E
D
I
A
L
Deep Posterior
Compartment
Lateral
Compartment
Superficial Posterior
Compartment

21. Tibialis Anterior

22. Tibialis Anterior
arises from
lateral surface of shaft of
Tibia
attaches to
Medial Cuneiform
1st
Metatarsal base

23. Tibialis anterior muscleTibialis anterior muscle
Tibialis anterior tendonTibialis anterior tendon
Tibialis Anterior
arises from
lateral surface of shaft of
Tibia
attaches to
Medial Cuneiform
1st
Metatarsal base

24. Tibialis Anterior
Dorsiflexes ankle joint
Inverts foot
Tibialis anterior muscleTibialis anterior muscle
Tibialis anterior tendonTibialis anterior tendon

25. Extensor Digitorum Longus

26. Extensor Digitorum Longus
Arises from
Fibula
Interosseous Membrane

27. Extensor Digitorum Longus
Arises from
Fibula
Interosseous Membrane
The tendon divides into four slips and
these insert into the
dorsal expansions of toes 2-5

28. The tendon divides into four slips and
these insert into the
dorsal expansions of toes 2-5

29. Extensor Digitorum Longus
Dorsiflexes the ankle joint
Extends the toes

30. Extensor Hallucis Longus

31. Extensor Hallucis Longus
Arises from the
Fibula

32. Extensor Hallucis Longus
Arises from the
Fibula
Inserts onto the
Distal Phalanx of Big Toe

33. Tendon of
Extensor Hallucis Longus
Extensor Hallucis Longus
Extends the Big Toe
Dorsiflexes Ankle Joint

34. Peroneus Tertius
also known as
Fibularis Tertius

35. Peroneus Tertius
Arises from the
Fibula

36. Peroneus Tertius
Arises from the
Fibula
Inserts onto dorsum of
5th
metatarsal base

37. Peroneus Tertius
Tendon of Peroneus Tertius

38. Tendon of Peroneus Tertius
Peroneus Tertius
Everts foot
Dorsiflexor of the foot

39. Extensor Retinacula are thickenings
of deep fascia that prevent
‘bowstringing’ of the extensor
tendons

40. Extensor Retinacula are thickenings
of deep fascia that prevent
‘bowstringing’ of the extensor
tendons
Superior extensor retinaculum
Inferior extensor retinaculum

41. Nerve Supply

42. All the muscles in the Anterior Compartment
are supplied by the
Deep Peroneal Nerve

43. Deep Peroneal Nerve
Injury to this nerve causes a condition
known as ‘foot drop’
The foot can no longer be dorsiflexed which
causes difficulty in walking
The knee has to be lifted much higher in order to
prevent the foot from dragging on the ground
This is called a ‘High Stepping Gait’

44. Summary of Muscles

45. Anterior Leg
Tibialis Anterior
Origin Lateral condyle of tibia, proximal
2/3rds lateral surface tibia,
interosseous membrane
Insertion Medial and plantar surfaces of
medial cuneiform and base of
first metatarsal
Action Dorsiflexor of ankle, invertor of
foot
Nerve Supply Deep peroneal nerve (L4, L5)
Blood Supply Anterior tibial artery

46. Extensor Digitorum Longus
Origin Head of fibula, upper 2/3 anterior
fibular shaft, interosseous
membrane
Insertion Splits into 4 tendons distally;
these insert onto dorsum of
middle and distal phalanges of
toes 2-5. Part of extensor
expansion complex
Action Extends toes 2 - 5 and dorsiflexes
ankle
Nerve Supply Deep peroneal nerve (L5, S1)
Blood Supply Anterior tibial artery
Anterior Leg

47. Extensor Hallucis Longus
Origin Anterior surface of the fibula,
interosseous membrane
Insertion Base of distal phalanx great toe
Action Extends great toe and dorsiflexes
ankle
Nerve Supply Deep peroneal nerve (L5, S1)
Blood Supply Anterior tibial artery
Anterior Leg

48. Anterior Leg
Fibularis Tertius
Origin Distal 1/3rd
anterior surface of
fibula
Insertion Base of dorsal aspect 5th
metatarsal
Action Dorsiflexes foot;
everts foot weakly
Nerve Supply Deep peroneal nerve (L5, S1)
Blood Supply Anterior tibial artery