S2 Nerve Root (S2)

Authors

Affiliations

Nate Yomogida, B.S., SPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, B.S., SPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Nerve roots extending from the spinal cord¹

Peripheral Nerve Supply

Nerve	Roots	Motor Innervation	Cutaneous Innervation
Posterior Cutaneous Nerve of the Thigh
Sciatic N.
Common Fibular N.	L4, L5, S1, S2
Tibial N.	L4, L5, S1, S2, S3
Pudendal N.	S2, S3, S4

Muscle Supply

Motor Innervation

Muscle	Origin	Insertion	Innervation	Action
Abductor digiti minimi (Foot)	Plantar aponeurosis	5th metatarsal tuberosity	S2 - S3	5th Toe: MTP Abduction Arch support: Longitudinal arch support
Abductor hallucis	Medial calcaneal tuberosity Plantar aponeurosis Flexor retinaculum	Medial aspect of 1st Proximal phalanx	Medial Plantar n. S1 - S2	1st Toe: MTP Flexion, MTP Abduction Arch support: Longitudinal arch support
Abductor digiti minimi	Medial tubercle of calcaneal tuberosity Cuboid Lateral cuneiforms 3-5th MTP joints Deep transverse metatarsal lig.	Base of 5th proximal phalanx Base of 1st proximal phalanx (via common tendon)	Lateral Plantar n. Lateral Plantar n. (Deep branch) S1 - S3	5th Toe: MTP Flexion 1st MTP: Flexion, Adduction Arch Support: *Transverse head* supports transverse arch, *Oblique head* supports longitudinal arch
Biceps femoris long head	Ischial tuberosity Sacrotuberous lig. (Common head with semitendinosus)	Fibular head	Tibial n. L5 - S2	Hip: Extension Knee: Flexion, ER Pelvis: Sagittal stabilization
Biceps femoris short head	Lateral lip of Linea aspera	Fibular head	Common Fibular n. L5 - S2	Knee: Flexion, ER
Dorsal interossei (4 muscles)	1-5 metatarsals (two heads on opposing sides)	Medial aspect of 2nd proximal phalanx base Lateral aspect of 2nd-4th proximal phalanx bases 2-4 Toes at Dorsal aponeurosis	Lateral plantar n. S2 - S3	2nd-4th Toes: MTP Flexion, MTP 3-4 abduction, PIP Extension, DIP Extension
Flexor digiti minimi brevis (foot)	Base of 5th Metatarsal Long plantar lig.	Base of 5th proximal phalanx	Lateral Plantar n. (superficial branch) S2 - S3	5th MTP Flexion
Flexor digitorum brevis	Medial tubercle of calcaneal tuberosity Plantar aponeurosis	Sides of middle phalanx 2-5	Medial Plantar n. S1 - S2	2nd-5th Toe: MTP Flexion, PIP Flexion Arch support: Longitudinal arch support
Flexor digitorum longus	Middle 1/3 of posterior surface of Tibia	Bases of 2-5 Distal Phalanges	Tibial n. L5 - S2	TCJ: PF STJ: Inversion 2nd-5th Toe: MTP Flexion, PIP Flexion, DIP Flexion
Flexor hallucis brevis	Cuboid Lateral cuneiforms Plantar calcaneocuboid lig.	Medial Sesamoid bone Lateral Sesamoid bone	Lateral Plantar n. Medial Plantar n. S1 - S2	MTP Flexion Supports Longitudinal Arch
Flexor hallucis longus	Posterior distal 2/3 of Fibula IO membrane	Base of 1st Distal Phalanx	Tibial n. L5 - S2	TCJ: PF STJ: Inversion 1st Toe: MTP Flexion, IP Flexion
Gastrocnemius	Superior-posterior aspect of Medial Femoral Condyle Lateral surface of Lateral Femoral Condyle	Calcaneal tuberosity via Achilles' Tendon	Tibial n. S1 - S2	TCJ: PF Knee: Flexion
Gluteus Maximus	Sacrum (dorsal surface, lateral part) Ilium (gluteal surface, posterior part) Thoracolumbar fascia sacrotuberous lig.	IT Band Gluteal tuberosity	Inferior gluteal n. L5 - S2	Entire mm.: Extension, ER (when <60° HF) Upper fibers: Abduction, IR (when &gt60° HF) Lower fibers: Adduction
Lumbricals (Foot)	FDL tendons (medial borders)	2-5th toes at dorsal aponeurosis	Medial Plantar n. Lateral Plantar n. S2 - S3	2nd-5th Toes: MTP Flexion, PIP Extension, DIP Extension
Opponens digiti minimi	Long plantar lig. *Fibularis longus* plantar tendon sheath	5th metatarsal	Lateral Plantar n. (superficial branch) S2 - S3	Pulls 5th metatarsal in plantar and medial direction
Piriformis	Anterior Sacrum	Apex of the Greater Trochanter	Sacral Plexus Direct Br. S1 - S2	Hip (at <60° flexion): ER Hip: Abduction, Extension, Stabilization Hip (at ≥60° flexion): IR
Plantar interossei (3 muscles)	Medial border of 3rd-5th metatarsals	Medial aspect of 3rd-5th proximal phalanx	Lateral plantar n. S2 - S3	3rd-5th Toes: MTP Flexion, MTP Adduction, PIP Extension, DIP Extension
Plantaris	Lateral epicondyle of Femur	Calcaneal tuberosity	Tibial n. S1 - S2	Knee: *negligble* Flexion TCJ: PF Proprioception: Organ of proprioception for the plantarflexors
Quadratus plantae	Calcaneal tuberosity (medial and plantar borders)	Tendons of FDL (lateral borders)	Lateral Plantar n. S1 - S3	Redirects and augments pull of the FDL
Semimembranosus	Ischial tuberosity	Medial tibial condyle Oblique popliteal lig. Popliteus fascia	Tibial n. L5 - S2	Hip: Extension Knee: Flexion, IR Pelvis: Sagittal stabilization
Semitendinosus	Ischial tuberosity Sacrotuberous lig. (common head with biceps femoris long head)	Pes anserine	Tibial n. L5 - S2	Hip: Extension Knee: Flexion, IR Pelvis: Sagittal stabilization
Soleus	Posterior Fibula Posterior Tibia	Calcaneal tuberosity via Achilles' Tendon	Tibial n. S1 - S2	TCJ: PF Lower leg: Stabilization

Dermatome

Figure 2: Dermatomal cutaneous distribution¹

Figure 3: Dermatomal cutaneous distribution (Posterior)¹

Examination

DTR

• Achilles Reflex (S1, S2)

References

1.

Gray H. Anatomy of the Human Body. 20th ed. (Lewis WH, ed.). Lea & Febiger; 1918. https://www.bartleby.com/107/