What is the approach to evaluating a patient with coccyx pain, considering their medical history, physical examination, and potential underlying causes?

Evaluation of Coccyx Pain

Begin with a detailed pain history focusing on trauma, sitting intolerance, and pain location, followed by physical examination with direct palpation of the coccyx, then obtain dynamic lateral radiographs (standing and sitting positions) as the first-line imaging to assess for abnormal mobility, which is the most common pathological finding in 70% of coccydynia cases. 1, 2

History Taking

Pain Characteristics

• Document the onset, quality, intensity, and duration of pain, with specific attention to whether symptoms worsen with sitting or during transitions from sitting to standing 3, 4
• Ask about trauma history, as this is the most common etiologic factor for coccydynia 1, 5
• Assess for sitting intolerance, which significantly impacts quality of life 1, 4
• Determine if pain is midline, located below the sacrum and above the anus 4

Medical and Social History

• Review surgical history, current medications, and history of obesity or activities involving prolonged sitting, bicycling, rowing, or riding, as these contribute to chronic static and dynamic overload of the coccyx 3, 1
• Screen for history of cancer, unexplained weight loss, fever, or recent infection to rule out serious pathology 6, 7
• Document female sex, as this is a risk factor for coccydynia 2

Psychosocial Assessment

• Evaluate for depression, anxiety, and impact on activities of daily living, as psychosocial factors can predict chronicity 3

Physical Examination

Focused Musculoskeletal and Neurological Examination

• Perform direct palpation of the coccyx, which typically reveals focal tenderness in coccydynia 4
• Conduct digital rectal examination to assess coccygeal mobility and tenderness 3
• Evaluate for extracoccygeal causes including pilonidal cyst, perianal abscess, hemorrhoids, and lumbosacral spine disorders 1
• Assess sacroiliac joints, piriformis muscle, and pelvic organs as potential pain sources 1

Imaging Strategy

First-Line Imaging

• Obtain dynamic lateral radiographs of the coccyx in both standing and sitting positions to evaluate for abnormal mobility, which is present in 70% of coccydynia patients 1, 2
• Look for hypermobility defined as more than 25% posterior subluxation while sitting or more than 25° flexion while sitting; significant hypermobility is defined as more than 35° posterior subluxation 2
• Assess for morphologic parameters including Type II coccyx morphology, subluxation of intercoccygeal joints, and presence of bony spicules 2
• Evaluate for coccyx fractures classified as flexion type 1, compression type 2, or extension type 3 2

Advanced Imaging

• Consider MRI or CT when plain radiographs are inconclusive but clinical suspicion remains high, as these modalities can reveal coccygeal pathology not visible on X-ray 8, 2
• MRI is useful for evaluating disc degeneration at sacrococcygeal and intercoccygeal segments, osteomyelitis, and tumors 1
• CT provides detailed assessment of bony anatomy and morphometric features 2

Diagnostic Confirmation

Diagnostic Injections

• Confirm coccygeal origin of pain through injections of local anesthetic into structures that may be pain sources, including the sacrococcygeal disc, first intercoccygeal disc, Walther's ganglion, and muscle attachments around the coccyx 1
• These diagnostic blocks help differentiate coccygeal from extracoccygeal causes 1

Common Pitfalls

• Do not overlook the coccyx region during routine imaging, as coccydynia is one of the most overlooked symptoms in clinical practice 2
• Recognize that in 30% of patients, no cause can be found (idiopathic coccydynia), and these patients often present with long-standing pain and multiple physician visits 1, 2
• Avoid attributing pain solely to imaging findings without clinical correlation, as morphologic variations may be incidental 7
• Remember that abnormal mobility can result from both acute injury and chronic overload 1