WEEK 4: The leg & foot, Clinical Correlations

Question 1

State the 3 main compartments of the leg muscles and their associated function and innervation.

Answer 1

1. ANTERIOR COMPARTMENT
   -Dorsiflexion
   -Toe extension
   -Deep fibular nerve
2. Medial compartment
   -Plantar flexion
   -Eversion
   -Superficial tibial nerve
3. POSTERIOR COMPARTMENT
   -Plantar flexion
   -Tibial nerve

Question 2

Outline the landmarks on the tibia and anatomic function if possible.

Answer 2

-It is large, located medially and weight bearing

PROXIMAL
-Intercondylar tubercle (medial and lateral)
-Condyles (medial and lateral)

DISTAL
-Tibial tuberosity: Attachment of the tibial collateral ligament
-Medial malleolus (distally)

-Weight is transmitted to talus
-Shin bone: anterior surface of the leg, no muscle attachments

CLINICAL RELEVANCE

Question 3

Outline the landmarks on the fibula and anatomic function if possible.

Answer 3

-Slender lateral bone
-No articulation with femur at the knee joint
-Has no weight bearing activity
-Stabilizes the ankle joint
-Provides attachment for muscles

PROXIMAL
-Head
-Neck prone to injuries

DISTAL
-Lateral malleolus

• There are 2 articulation, proximal and distal between tibia and fibula forming TIBIOFIBULAR JOINT.
• The two bones are also held together by interosseous membrane.

Question 4

State the clinical relevance connected to the FIBULA.

Answer 4

-Fibula neck fracture: Injury to common fibula nerve which wraps around it resulting in leg drop
-Used for bone grafting

Question 5

List the anterior compartment muscles anterior their functions.

Answer 5

1. Tibialis Anterior
   Actions: Dorsiflexion and inversion of the foot.
   Innervation: Deep fibular nerve.
2. Extensor Digitorum Longus
   Attachments:
   Originates from the lateral condyle of the tibia and the medial surface of the fibula.
   The fibres converge into a tendon, which travels onto the dorsal surface of the foot.
   The tendon splits into four and each tendon inserts onto a toe.
   Actions: Extension of the lateral four toes, and dorsiflexion of the foot.
   Innervation: Deep fibular nerve.
3. Extensor Hallucis Longus
   The extensor hallucis longus is positioned deep to tibialis anterior and extensor digitorum longus. Its tendon emerges from between the two muscles to insert onto the big toe.
   * Attachments: Originates from the medial surface of the fibular shaft. The tendon crosses anterior to the ankle joint and attaches to the base of the distal phalanx of the great toe.
   * Action: Extension of the great toe and dorsiflexion of the foot.
   * Innervation: Deep fibular nerve.
4. Fibularis Tertius
   The fibularis tertius muscle is thought to arise from the most distal part of the extensor digitorum longus.
   It is not present in all individuals.
   * Attachments: Originates with the extensor digitorum longus from the medial surface of the fibula.
   * Its tendon descends onto the dorsal surface of the foot and attaches to the fifth metatarsal.
   * Actions: Eversion and dorsiflexion of the foot.
   * Innervation: Deep fibular nerve.

Question 6

Discuss the clinical relevance related to the anterior compartment muscles.

Answer 6

Clinical Relevance: Footdrop

Footdrop is a clinical sign that refers to an inability to dorsiflex the foot at the ankle joint – resulting in the foot “dropping” under the influence of gravity.

It indicates paralysis or weakness of the muscles in the anterior compartment of the leg, and typically occurs because of damage to the common fibular nerve (from which the deep fibular nerve arises)

The inability to dorsiflex the foot can interfere with walking – as the affected foot drags along the ground. To circumvent this, the patient can flick the foot outwards while walking – known as an ‘eversion flick‘.

Question 7

Discuss the 2 lateral compartment muscles: insertion, innervation and action.

Answer 7

1. FIBULARIS LONGUS
   The fibularis longus is the larger and more superficial muscle within the compartment.
   * Attachments
   o The fibularis longus originates from the superior and lateral surface of the fibula and the lateral tibial condyle.
   o The fibres converge into a tendon, which descends into the foot, posterior to the lateral malleolus.
   o The tendon crosses under the foot, and attaches to the bones on the medial side, namely the medial cuneiform and base of metatarsal I.
   * Actions: Eversion and plantarflexion of the foot. Also supports the lateral and transverse arches of the foot.
   * Innervation: Superficial fibular (peroneal) nerve.
2. Fibularis Brevis
   The fibularis brevis muscle is deeper and shorter than the fibularis longus.

• Attachments:
  o Originates from the inferolateral surface of the fibular shaft. The muscle belly forms a tendon, which descends with the fibularis longus into the foot.
  o It travels posteriorly to the lateral malleolus, passing over the calcaneus and the cuboidal bones.
  o The tendon then attaches to a tubercle on the 5th metatarsal.
• Actions: Eversion of the foot.
• Innervation: Superficial fibular (peroneal) nerve.

Question 8

State the clinical relevance related to the fibularis longus muscle: Lateral compartment muscle.

Answer 8

Clinical Relevance: Locating the Common Fibular Nerve

The common fibular nerve can be a difficult structure to identify.
However, it can be located using the fibularis longus as an anatomical landmark.

There is a small space between the parts of the fibularis longus that originate from the head of the fibula, and the neck of the fibula. The common fibular nerve passes through this gap and is easily identified.

After passing through the gap, the nerve terminates by bifurcating into two terminal branches: the deep and superficial fibular nerve.