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Crus of penis

The crura of the penis are paired structures that represent the posterior extensions of the corpora cavernosa. Each crus anchors the penis firmly to the ischiopubic rami, forming part of the root of the penis. They play a vital role in penile rigidity during erection by transmitting forces from the attached erectile tissues. The crura are covered by the ischiocavernosus muscles, which help maintain penile erection by compressing the venous outflow.

They are clinically relevant in trauma, erectile dysfunction, Peyronie’s disease, and surgical procedures involving the perineum or penile prosthesis placement.

Synonyms

  • Penile crus

  • Corpora cavernosa crus

  • Root of penis (lateral portion)

Origin, Course, and Attachments

  • Origin: Each crus arises from the posterior end of a corpus cavernosum

  • Course:

    • Extends posteriorly and laterally from the root of the penis

    • Anchors along the ischiopubic rami

    • Enclosed by the ischiocavernosus muscle, which aids in erection

  • Insertion/Attachment: Firmly attached to the medial surface of the ischiopubic ramus; continues anteriorly as the corpus cavernosum

Relations

  • Anteriorly: Join at the midline to form the corpora cavernosa of the penile shaft

  • Posteriorly: Related to perineal membrane and pelvic floor musculature

  • Laterally: Covered by the ischiocavernosus muscle

  • Inferiorly: Lies adjacent to superficial perineal fascia and vessels

  • Superiorly: Related to perineal body and urogenital diaphragm structures

Function

  • Provides anchorage and stability to the penis during erection

  • Forms part of the erectile tissue responsible for penile rigidity

  • Covered by ischiocavernosus muscles, which compress venous outflow to sustain erection

  • Assists in direction and support of the penile shaft during sexual function

Clinical Significance

  • Trauma: Pelvic fractures or perineal trauma may disrupt crus attachment

  • Erectile dysfunction: Injury or fibrosis of crura can impair erection

  • Peyronie’s disease: Fibrous plaques may extend toward the root, involving the crus

  • Surgical relevance: Important landmark in perineal surgery, penile prosthesis placement, and reconstructive urology

  • Oncology: May be involved in local extension of penile or pelvic tumors

MRI Appearance

T1-weighted images:

  • Crus appears as intermediate signal intensity, similar to other erectile tissues

  • Surrounded by bright fat, which enhances contrast

  • Fibrosis or chronic scarring appears darker

T2-weighted images:

  • Crus shows intermediate to mildly hyperintense signal

  • Vascular sinusoids within corpora cavernosa may appear heterogeneous depending on filling

  • Edema or inflammation: increased brightness

STIR (Short Tau Inversion Recovery):

  • Normal crus appears as mildly hyperintense signal signal

  • Edematous or inflamed crus: bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Crus enhances due to vascular erectile tissue

  • Enhancement is homogeneous in normal state

  • Asymmetry or focal heterogeneous enhancement may indicate tumor, fibrosis, or trauma

3D T2 SPACE / CISS:

  • Crus shows intermediate to mildly hyperintense signal compared to muscle

  • Surrounded by bright fat, providing excellent delineation of anatomy

  • Useful for defining relations with ischiopubic rami and adjacent muscles

CT Appearance

Non-Contrast CT:

  • Crus appears as soft tissue density along the ischiopubic rami

  • Better visualized when surrounded by perineal fat planes

  • Calcification or fibrosis may appear as hyperdense foci

Post-Contrast CT:

  • Crus enhances moderately due to vascular erectile tissue

  • Pathology (inflammation, tumor infiltration, trauma) may cause asymmetric or irregular enhancement

  • Hematoma appears as localized high attenuation before contrast and may not enhance centrally

MRI image

Crus of penis mri axial anatomy image-img-00000-00000

CT image

Crus of penis ct axial anatomy image-img-00000-00000