S3 Nerve Root (S3)

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

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 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
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
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
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
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

References

1.

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