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Posterior division of obturator nerve (Posterior branch of obturator nerve)

The posterior division of the obturator nerve is a terminal branch of the obturator nerve, arising in the pelvis and traveling into the medial thigh. It passes deep within the thigh and supplies key adductor muscles along with articular branches to the knee. Its deep position and close relation to the adductor magnus, adductor brevis, and obturator externus make it clinically and surgically significant.

Synonyms

  • Posterior branch of obturator nerve

  • Deep division of obturator nerve

  • Obturator nerve (posterior trunk)

Course

  • Originates from the obturator nerve after it passes through the obturator canal

  • Runs posterior to the adductor brevis and anterior to the adductor magnus

  • Travels downward in the medial thigh, giving muscular and articular branches

  • Ends by contributing to the subsartorial plexus and sending articular fibers to the posterior knee joint capsule

Relations

  • Anteriorly: Adductor brevis muscle

  • Posteriorly: Adductor magnus muscle

  • Laterally: Obturator externus

  • Medially: Femoral vessels (proximally) and medial thigh compartment

Branches

  • Muscular branches:

    • To the obturator externus

    • To the adductor magnus (hamstring portion)

  • Articular branch:

    • To the knee joint, passing through the adductor hiatus

Function

  • Provides motor innervation to the obturator externus and adductor magnus (hamstring part)

  • Contributes to hip joint stability via obturator externus innervation

  • Supplies articular sensation to the knee joint (posterior capsule)

Clinical Significance

  • May be involved in entrapment neuropathy causing medial thigh pain

  • Injury during pelvic or hip surgery may cause weakness of adduction and sensory disturbance

  • Contribution to referred pain to the knee via articular branches

  • Target in nerve blocks for hip and knee surgeries

MRI Appearance

T1-weighted images:

  • Nerve appears as a thin, linear structure with low-to-intermediate signal intensity within the medial thigh fat planes

T2-weighted images:

  • Normal nerve shows intermediate signal intensity

  • Injured or inflamed nerve demonstrates increased bright signal intensity

STIR (Short Tau Inversion Recovery):

  • Normal nerve is low-to-intermediate signal

  • Pathological changes (neuritis, entrapment, trauma) show bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal nerve enhances minimally or not at all

  • Inflamed or neoplastic nerve may enhance focally or diffusely

CT Appearance

Non-Contrast CT:

  • Nerve is not directly visualized but inferred by its anatomical course between adductor brevis and magnus

  • Surrounding fat planes help in indirect identification

Post-Contrast CT:

  • The nerve itself does not enhance significantly

  • Pathology (nerve sheath tumors, inflammatory changes) may cause focal soft tissue thickening or enhancement in its expected location

MRI image

Posterior division of obturator nerve MRI axial anatomy image-img-00000-00000

MRI image

Posterior division of obturator nerve MRI axial anatomy image-img-00000-00000_00001

MRI image

Posterior division of obturator nerve MRI axial anatomy image-img-00000-00000_00002

MRI image

Posterior branch of obturator nerve