see also:

• The adult with back pain in the ED

• buttock pain is not an uncommon presentation, it may be:
  • isolated pain
  • associated with back pain and sciatica
  • associated with abdominal pain such as with abdominal aortic aneurysm (AAA)
  • primarily only on walking - buttock claudication

• impaired blood flow from internal iliac artery
  • abdominal aortic aneurysm (AAA)
  • abdominal aorta stenosis - likely to cause bilateral symptoms
  • internal iliac artery stenosis
  • complication of IIA stent/endovascular repair including gluteal compartment syndrome

• gluteal muscle strain
• ischiogluteal bursitis
  • weaver's bottom
• hamstring tendonitis
• piriformis syndrome - muscle spasm or haematoma in the piriformis muscle
  • can also irritate the sciatic N causing sciatica
  • pain increases walking up stairs long walks, running, and with prolonged sitting
  • there may be reduced ROM of the hip joint
• shingles
• haematoma
• abscess
• pyomyositis gluteal muscle
  • usually haematogenous seeding of Staph. aureus, eg. IVDU
  • higher risk in immunocompromised
  • MRI is best diagnostic modality
  • https://www.bmj.com/content/357/bmj.j2400
• sacro-iliitis - pain and tenderness over the PSIS
• hip pain
  • avascular necrosis of the femoral head
  • osteoarthritis
  • bursitis
• rarely, persistent sciatic artery aneurysm which is a rare congenital anomaly

• local infection
  • pilonidal sinus / abscess
• muscle/ ligament strain
• sacrococcygeal joint pain
  • arthritis
  • disc issues
• sacral injury
• sacral stress fracture
• radicular referred pain may uncommonly be central sacral pain
• endometriosis
• pelvic or urethral neoplasia

• the coccyx¹⁾:
  • anatomy:
    • 3 to 5 fused segments with variability in the structure of their intervertebral joints: from intact discs resembling lumbar intervertebral discs to intermediate disc structures with cystic or fibrotic changes to synovial joints and may also be fused
    • bordered anteriorly by the levator ani muscle and the sacrococcygeal ligament
    • lateral edges serve as insertion sites antero-posteriorly for the coccygeal muscles, the sacrospinous ligament, the sacrotuberous ligament, and fibers of the gluteus maximus muscle
    • inferiorly, the iliococcygeus muscle tendon inserts onto the tip of the coccyx
    • normal range of motion at sacro-coccygeal joint should be approximately 13 degrees
  • has several important functions:
    • the ligaments and muscles inserting onto it help support the pelvic floor and contribute voluntary bowel control
    • provides weight bearing support in the seated position forming a tripod with the two ischial tuberosities
• traumatic pain
  • may be due to bruising, fracture or dislocation of the coccyx
  • this is most likely due to a fall onto buttocks but may occur when giving birth
  • it may also be caused from repetitive or prolonged sitting on hard narrow or uncomfortable surfaces
• non-traumatic pain:
  • aetiology:
    • degenerative joint or disc disease
    • hypermobility or hypomobility of the sacrococcygeal joint
    • infectious etiology
    • variants of coccygeal morphology
    • pelvic floor muscle spasms
    • referred pain (radicular) - S4, S5 or Co1 (the ganglion impar (located anterior to the coccyx) can mediate pain to the coccygeal region)
    • somatization disorders
    • rarely, neoplasms may cause it
  • epidemiology:
    • 5x more common in women
    • obesity is a risk factor
    • rapid weight loss can also be a risk factor because of the loss of mechanical cushioning