What are the causes of acute central coccygeal pain (coccydynia) in a 36‑year‑old woman with onset yesterday and no preceding trauma?

Causes of Acute Central Coccygeal Pain (Coccydynia)

In a 36-year-old woman with acute coccydynia of one day's duration and no preceding trauma, the most likely causes are idiopathic (30% of cases), abnormal coccygeal mobility from chronic overload, or less commonly, infection, tumor, or referred pain from pelvic/visceral structures 1, 2.

Primary Etiologic Categories

Mechanical/Structural Causes (Most Common)

• Abnormal coccygeal mobility (hypermobility, subluxation, or luxation) accounts for approximately 70% of cases with identifiable pathology 2

  • Can result from chronic static/dynamic overload: obesity, prolonged sitting, bicycling, rowing, or riding
  • May develop without acute trauma through repetitive microtrauma

• Degenerative changes: disc degeneration at sacrococcygeal or intercoccygeal segments 2

• Anatomical variations: developmental anomalies of coccygeal vertebrae (rare but documented) 3

• Coccygeal spicule (bony excrescence) causing local irritation 2

Idiopathic (30% of Cases)

When no identifiable cause is found despite thorough evaluation, this is termed idiopathic coccydynia 2. This represents a significant proportion and should be considered a diagnosis of exclusion.

Infectious/Inflammatory Causes

• Osteomyelitis of the coccyx 2
• Pilonidal cyst or perianal abscess 2

Neoplastic Causes

• Primary or metastatic tumors involving the coccyx 4, 2
• Must be excluded in all cases, particularly with red-flag features

Referred Pain Sources

Pain may originate from structures other than the coccyx itself 2, 5:

• Pelvic organs: rectum, sigmoid colon, urogenital system disorders
• Lumbosacral spine: disc herniation, radiculopathy
• Sacroiliac joints: dysfunction or inflammation
• Piriformis muscle: spasm or syndrome
• Hemorrhoids or other anorectal pathology

Key Clinical Distinction

Critical caveat: The absence of trauma does not exclude mechanical coccygeal pathology 6, 2. Many patients develop abnormal coccygeal mobility through cumulative microtrauma from occupational or lifestyle factors rather than a single traumatic event.

Diagnostic Approach for Non-Traumatic Acute Onset

1. History must specifically assess:

   • Occupational factors (prolonged sitting, cycling, rowing)
   • Recent childbirth (even remote, as effects can be delayed)
   • Constitutional symptoms (fever, weight loss suggesting infection/malignancy)
   • Bowel/bladder/gynecologic symptoms (suggesting referred pain)

2. Physical examination should include:

   • Manual palpation of coccyx (external and rectal examination) to reproduce pain 5
   • Assessment for pilonidal cyst, perianal pathology
   • Neurologic examination if referred pain suspected

3. Initial imaging:

   • Standard lateral radiographs to exclude fracture, tumor, infection 7
   • Dynamic sitting-standing radiographs if mechanical pain suspected and symptoms persist, as these reveal pathologic motion not visible on static films 4, 7
   • MRI or CT reserved for red-flag features, suspected neoplasm/infection, or inconclusive basic imaging 7

Important Clinical Pitfall

Do not assume pain without trauma is "functional" or psychogenic. The majority of non-traumatic coccydynia has identifiable mechanical or pathologic causes when properly evaluated with dynamic imaging and systematic exclusion of referred pain sources 2, 5.