Lower Limb Anatomy: Leg Compartments and Nerve Supply

This set of vocabulary flashcards covers the anatomical compartments of the leg, including their muscle contents, nerve supplies, distal attachments, and functional roles in gait and movement.

Extrinsic foot muscles

Muscles with their muscle belly located outside the foot in the leg and a long tendon or distal attachment located inside the foot.

Tarsals

There are $7$ of these bones located in the ankle and foot.

Metatarsals

There are $5$ of these bones located in the midfoot.

Phalanges

There are $14$ of these bones located in the digits of the foot.

L1 Spinal Level

Nerve root responsible for sensation in the anterior hip and groin.

L2,3 Myotomes

Spinal levels responsible for the motor function of the iliopsoas and quadriceps.

L4 Sensory Area

The region of the anteromedial leg.

Tibial Nerve Course

Passes between the heads of the gastrocnemius, anterior to the arch of soleus with the popliteal artery, and descends to lie between the calcaneus and medial malleolus.

Common Fibular Nerve Location

Winds lateral to the fibular neck, deep to the fibularis longus, making it very superficial and vulnerable to damage from ice application.

Superficial Posterior Compartment Muscles

Consists of the Gastrocnemius and Soleus, both of which attach distally to the calcaneus via the calcaneal/Achilles tendon.

Talocrural Dorsiflexors

Muscles that pass anterior to the medial malleolus.

Talocrural Plantarflexors

Muscles that pass posterior to the medial malleolus.

Subtalar Invertors

Muscles that pass medial to the oblique axis of the subtalar joint.

Subtalar Evertors

Muscles that pass lateral to the oblique axis of the subtalar joint.

Deep Posterior Compartment Muscles

A group of $3$ muscles including the flexor digitorum longus, tibialis posterior, and flexor hallucis longus.

Tibialis Posterior Distal Attachment

Attaches to the navicular, cuneiforms, cuboid, and the bases of the metatarsals.

Deep Posterior Compartment Functions

Acts as prime movers for toe flexion and inversion/supination, supports the medial longitudinal arch, and is involved in push off.

Anterior Compartment Muscles (Pretibials)

A group of $4$ muscles (Tibialis anterior, Extensor digitorum longus, Extensor hallucis longus, and Fibularis tertius) supplied by the deep fibular nerve.

Anterior Compartment Primary Functions

Prime movers for dorsiflexion and toe extension; responsible for shock absorption at heel strike and foot clearance in the swing phase of gait.

Lateral Compartment Muscles

Consists of the Fibularis longus and Fibularis brevis, which serve as the prime movers for eversion.

Lateral Compartment Nerve Supply

Supplied by the superficial fibular nerve.

Avulsion Fracture of Base of $5^{th}$ Metatarsal

An injury occurring during an inversion sprain where the fibularis brevis tendon pulls its attachment off the bone.

Compartment Syndrome

A condition where pressure builds within the strong fascia of the leg, potentially compressing nerve and vascular structures; sometimes colloquially referred to as "shin splints."

L4 Myotome

Responsible for dorsiflexion and inversion.

L5 Myotome

Responsible for great toe extensions.

S1 Myotome

Responsible for plantarflexion.

S2 Myotome

Responsible for long toe flexors.