L3 Nerve Root (L3)

Authors

Affiliations

Nate Yomogida, PT, DPT

Doctor of Physical Therapy

B.S. in Kinesiology

Chloë Kerstein, PT, DPT

Doctor of Physical Therapy

B.A. in Neuroscience

Figure 1: Nerve roots extending from the spinal cord¹

Innervation

Peripheral Nerves Originating From L3

Nerve	Roots	Motor Innervation	Cutaneous Innervation
Lateral Cutaneous Nerve of the Thigh	L2, L3
Obturator N.	L2, L3, L4
Femoral N.	L2, L3, L4

Femoral nerve

Femoral nerve L3 innervations

• Quadriceps
  • Rectus Femoris²
  • Vastus lateralis²
  • Vastus intermedius²
  • Vastus medialis²
  • Articularis Genus²

Muscle Innervation

Motor Innervation

Muscle	Origin	Insertion	Innervation	Action
Adductor brevis	Inferior pubic ramus	Linea aspera	Obturator n. L2 - L3	Hip: Adduction, Flexion, Extension Pelvis: Frontal stabilization, Sagittal stabilization
Adductor Longus	Superior pubis ramus Anterior side of Pubic Symphysis	Linea aspera	Obturator n. L2 - L4	Hip: Adduction, Flexion, Extension Pelvis: Frontal plane stabilization, Sagittal plane stabilization
Adductor Magnus	Inferior pubic ramus Ischial ramus Ischial tuberosity	Medial lip of Linea aspera Adductor tubercle	Obturator n. Tibial n. L2 - L4	Hip: Adduction, Flexion, Extension, IR Pelvis: Frontal stabilization, Sagittal stabilization
Articular genus	Anterior Femoral shaft	Suprapatellar recess of knee joint capsule	Femoral n. L2 - L4	Knee: Extension Knee Jt. Capsule: Retraction of the suprapatellar bursa to prevent entrapment
Gracilis	Inferior pubic ramus	Pes anserine	Obturator n. L2 - L3	Hip: Adduction, Flexion Knee: Flexion, IR
Iliacus	Iliac Fossa	Lesser Trochanter	Femoral n. L2 - L3	Hip: Flexion, ER L/S (UNIL contraction on fixed femur): I/L spine sidebend L/S (BIL contraction): Raises trunk from supine position
Obturator externus	Outer surface of Obturator membrane Adjacent bony boundaries	Trochanteric Fossa	Obturator n. L3 - L4	Hip: Adduction, ER Pelvis: Sagittal Stabilization
Pectineus	Pecten pubis	Pectineal line Proximal linea aspera	Femoral n. Obturator n. L2 - L3	Hip: ER, Adduction, *slight* Flexion Pelvis: Frontal plane stabilization, Sagittal plane stabilization
Psoas Major	T12-L4 and associated IV discs L1-L5 TP	Lesser Trochanter	Lumbar Plexus Direct Br. L1 - L3	Hip: Flexion, ER L/S (unilateral contraction with femur fixed): I/L spine sidebend L/S (bilateral contraction): Raises trunk from supine position
Psoas Minor	T12, L1 vertebrae (lateral aspect) and IVD	Pectineal Line Iliopubic ramus Iliac fascia Inguinal ligament	Spinal nn. L1 - L3	Trunk: Weak flexion
Rectus femoris	AIIS Acetabular roof	Tibial tuberosity via Patellar ligament	Femoral n. L2 - L4	Hip: Flexion Knee: Extension
Sartorius	ASIS	Pes anserine	Femoral n. L2 - L3	Hip: Flexion, ER, Abduction Knee: Flexion, IR
Vastus intermedius	Anterior Femoral shaft	Tibial tuberosity via Patellar ligament	Femoral n. L2 - L4	Knee: Extension
Vastus lateralis	Lateral lip of Linea aspera Lateral surface of Greater trochanter	Tibial tuberosity via Patellar ligament Tibial tuberosity and patella via Patellar retinacula	Femoral n. L2 - L4	Knee: Extension
Vastus medialis	Linea aspera Intertrochanteric line	Tibial tuberosity via Patellar ligament Patellar retinacula	Femoral n. L2 - L4	Knee: Extension

Dermatome

Figure 2: Dermatomal cutaneous distribution¹

Figure 3: Dermatomal cutaneous distribution (Posterior)¹

Examination

Deep Tendon Reflex

• Patella reflex (L2, L3, L4, but predominantly L4)

References

1.

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

2.

Gilroy AM, MacPherson BR, Wikenheiser JC, Voll MM, Wesker K, Schünke M, eds. Atlas of Anatomy. 4th ed. Thieme; 2020.