2d - Muscles in the Leg

Question 1

a) What spinal nerves supply the Lumbar Plexus?
b) What are the major nerves in the Lumbar Plexus?
c) What spinal nerves supply them?
d) What do they innervate?

Answer 1

a) L1 - L4 supply the Lumbar Plexus
b) Femoral and Obturator
c) L2 - L4 supply both nerves
d) Femoral = Anterior thigh
Obturator = Posterior thigh

Question 2

a) What spinal nerves supply the Sacral Plexus?
b) What are the major nerves of the Sacral Plexus?
c) What do they innervate?

Answer 2

a) L4 - S4 supply the Sacral Plexus
b) Gluteal and Sciatic, which branches to Tibial and Common Fibular, which branches to Deep and Superficial Fibular
c) Gluteal = Gluteal muscles
Tibial = Posterior leg, intrinsic foot muscles
Superficial fibular = Lateral leg
Deep fibular = Anterior leg

Question 3

Tibialis Anterior - Origin, Insertion, Action, and Innervation

Answer 3

Origin: Lateral surface of proximal tibia and interosseous membrane
Insertion: Medial cuneiform and 1st metatarsal
Primary action: Dorsiflexion and inversion
Innervation: Deep fibular

Question 4

Extensor Hallicis Longus - Origin, Insertion, Action, and Innervation

Answer 4

Origin: Middle of medial surface of fibula and interosseous membrane
Insertion: Base of distal phalanx of hallux
Primary action: Extension of hallux and dorsiflexion
Innervation: Deep fibular

Question 5

Extensor Digitorum Longus - Origin, Insertion, Action, and Innervation

Answer 5

Origin: Lateral condyle of tibia, proximal fibula, and interosseous membrane
Insertion: Middle and distal phalanges of digits 2 to 5.
Primary action: Extension of digits 2 to 5, and dorsiflexion.
Innervation: Deep fibular

Question 6

Fibularis Longus - Origin, Insertion, Action, and Innervation

Answer 6

Origin: Upper lateral surface of fibula and head of fibula
Insertion: Tendon wraps under the foot laterally to distally and inserts into base of 1st metatarsal
Primary action: Eversion, plantarflexion, and arch support
Innervation: Superficial fibular

Question 7

Fibularis Brevis - Origin, Insertion, Action, and Innervation

Answer 7

Origin: Lower 2/3 lateral surface of fibula
Insertion: Base of 5th metatarsal
Primary action: Eversion
Innervation: Superficial fibular

Question 8

Gastrocnemius - Origin, Insertion, Action, and Innervation

Answer 8

Origin: Two heads from medial and lateral condyles of femur
Insertion: Calcaneus via calcaneal tendon
Primary action: Plantarflexion and knee flexion
Innervation: Tibial

Question 9

Soleus - Origin, Insertion, Action, and Innervation

Answer 9

Origin: Soleal line, superior tibia and fibula, and interosseous membrane
Insertion: Calcaneus via calcaneal tendon
Primary action: Plantaflexion
Innervation: Tibial

Question 10

Plantaris - Origin, Insertion, Action, and Innervation

Answer 10

Origin: Lateral supracondylar ridge of femur
Insertion: Calcaneus via calcaneal tendon
Primary action: Plantar flexion and knee flexion
Innervation: Tibial

Question 11

Popliteus - Origin, Insertion, Action, and Innervation

Answer 11

Origin: Lateral femoral condyle and lateral meniscus
Insertion: Posterior surface of proximal tibia
Primary action: Stabilizes knee joint and unlocks knee from full extension
Innervation: Tibial

Question 12

Tibialis Posterior - Origin, Insertion, Action, and Innervation

Answer 12

Origin: Interosseous membrane, superior tibia, and superior fibula on posterior surfaces.
Insertion: Navicular
Primary action: Inversion, plantarflexion, and medial arch support
Innervation: Tibial

Question 13

Flexor Digitorum Longus - Origin, Insertion, Action, and Innervation

Answer 13

Origin: Posterior, medial surface of tibia
Insertion: Base of distal phalanx of digits 2-5
Primary action: Toe flexion of digits 2-5 and plantarflexion. Helps feet ‘grip’ the ground
Innervation: Tibial

Question 14

Flexor Hallicis Longus - Origin, Insertion, Action, and Innervation

Answer 14

Origin: Posterior fibula and interosseous membrane
Insertion: Distal phalanx of hallux
Primary action: Flexes hallux, inversion, and plantarflexion. The ‘push off’ muscle during walking
Innervation: Tibial

Question 15

What is Foot Drop?

Answer 15

Inability to dorsiflex.
Caused by damage to common fibular nerve, disc compressing L5 nerve root, or pathologies of sciatic nerve, lumbosacral plexus, spinal cord, or brain.

Question 16

Describe the Tarsal Tunnel.

Answer 16

Located on posteromedial ankle. The structures, from anterior to posterior, are:
Tibialis posterior tendon
Flexor digitorum longus tendon
Posterior tibial artery
Tibial nerve
Flexor hallicis longus tendon

Question 17

What’s Tarsal Tunnel Syndrome?

Answer 17

Entrapment of tibial nerve causing pain and altered sensation.
Insidious onset, often occurs in endurance athletes.