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CoccygeusEdit

The coccygeus is a small, triangular muscle that forms part of the posterior portion of the pelvic floor in humans and many other mammals. Also known as the ischiococcygeus, it sits behind the levator ani and contributes to the integrity and function of the pelvic diaphragm. As a component of the pelvic floor, the coccygeus helps to support pelvic viscera, resist increases in intra-abdominal pressure, and assist in stabilizing the sacrococcygeal region during body movements and childbirth.

Its anatomy is characterized by a relatively slender bundle of fibers that arise from the ischial spine and sweep medially and slightly upward to attach to the coccyx and the lower part of the sacrum. The muscle’s position and connections place it in close relation to the sacrospinous ligament and the fascial coverings of the pelvic outlet. Variation in size and exact attachments is common among individuals and among different mammalian species, reflecting adaptations to posture and locomotion.

The coccygeus works in concert with the rest of the pelvic floor, particularly the levator ani, to maintain continence and provide support for pelvic organs. It is traditionally described as contributing to flexion of the coccyx, particularly during defecation or parturition, and to stabilization of the sacrococcygeal joint when intra-abdominal pressure rises or when the trunk is loaded. The muscle’s action is subtle and synergistic, with the overall effect achieved through the coordinated contraction of several pelvic-floor muscles.

Anatomy

Origin and insertion

  • Originates from the ischial spine, with fibers that run superomedially.
  • Insertion points include the coccyx and the lower portion of the sacrum, with occasional slips contributing to adjacent pelvic fascia.

Morphology and relations

  • The coccygeus forms the posterior part of the pelvic floor in humans, lying anterior to the sacrospinous area and posterior to the levator ani.
  • It is in close proximity to structures such as the sacrococcygeal joint and the sacral plexus, and may blend with neighboring fascial layers in some individuals.

Innervation and blood supply

Function

  • Provides posterior support to the pelvic viscera as part of the pelvic diaphragm.
  • Assists in flexing and elevating the coccyx, particularly during defecation or childbirth.
  • Works together with the levator ani to stabilize the pelvic outlet and resist downward pressure.

Clinical significance

Coccydynia and pelvic floor considerations

  • Pain localized to the coccyx region, known as Coccydynia, can arise from trauma, repetitive strain, or referred pain from adjacent pelvic structures. While coccydynia is commonly discussed in relation to the coccyx itself, a coordinated dysfunction of the pelvic floor, including the coccygeus, can contribute to symptoms.
  • Injury or overuse of the coccygeus can accompany injuries to the surrounding pelvic-floor muscles, potentially affecting continence and pelvic stability.
  • Diagnosis typically involves clinical examination and imaging as needed to distinguish coccygeal or pelvic-floor etiologies from other causes of low back or gluteal pain.

Treatment and management

  • Conservative management emphasizes physical therapy aimed at improving pelvic-floor tone, flexibility, and coordination; posture and ergonomic adjustments, as well as pain control, are standard components.
  • In persistent cases, multidisciplinary evaluation may consider interventions that address adjacent musculoskeletal structures, pain management, or, rarely, surgical considerations when conservative options fail.

Evolution and comparative anatomy

  • The coccygeus is present across many mammalian lineages and represents a conserved element of the pelvic floor, though its size and exact attachments vary with locomotor and postural requirements.
  • In species with different pelvic configurations, the muscle can be more or less prominent, reflecting adaptations to bipedal or quadrupedal postures and the mechanical demands on the pelvic cavity.

See also