What causes lower back and coccyx pain when lying down that improves when standing or arching the back while lying on my stomach?

Positional Lower Back and Coccyx Pain: Diagnostic Approach and Management

Direct Answer

Your pain pattern—worsening when lying flat and relieving when standing or arching your back prone—suggests discogenic pain or anterior coccygeal subluxation rather than typical mechanical low back pain, which characteristically worsens with activity and improves with rest. 1

Understanding Your Pain Pattern

Your symptom pattern is atypical for common mechanical low back pain and warrants specific consideration:

• Typical mechanical low back pain worsens with activity and improves with rest, which is the opposite of your presentation 1
• Pain that improves with spinal extension (arching backward) and worsens with flexion (lying flat) suggests discogenic pathology or anterior displacement of coccygeal segments 2, 3
• Coccyx pain worsening in seated or recumbent positions occurs in 70% of patients with abnormal coccygeal mobility (hypermobility, anterior subluxation, or luxation) 2

Initial Diagnostic Steps

Red Flags to Exclude Immediately

Before attributing your pain to benign causes, you must exclude serious pathology:

• Cauda equina syndrome: Check for urinary retention (90% sensitivity), saddle anesthesia, bilateral leg weakness, or fecal incontinence 4
• Cancer indicators: History of cancer (increases probability to 9%), unexplained weight loss, failure to improve after 1 month, age >50 years 4
• Infection: Fever, night sweats, immunocompromised state, or intravenous drug use 5
• Progressive neurologic deficits: Worsening weakness, numbness, or motor deficits at multiple levels 4

Physical Examination Findings

Key examination maneuvers to identify the pain source:

• Direct palpation of the coccyx (performed rectally or externally) to assess for tenderness and abnormal mobility 2
• Dynamic assessment: Pain reproduction with transition from standing to sitting suggests coccygeal pathology 3
• Neurologic examination: Assess for radiculopathy with straight-leg raise test and lower extremity reflexes, strength, and sensation 5
• Lumbar range of motion: Pain relief with extension and worsening with flexion suggests discogenic origin 6

Imaging Strategy

When to Image

Do not obtain routine imaging for nonspecific low back pain without red flags, as it doesn't improve outcomes and may lead to unnecessary interventions 4, 1

However, your atypical positional pattern warrants selective imaging:

• Dynamic lateral radiographs of the coccyx (standing and sitting positions) are the initial study of choice to assess for abnormal coccygeal mobility, which is found in 70% of coccydynia patients 2
• MRI lumbar spine without contrast if symptoms persist beyond 6 weeks or if there are signs of nerve root irritation, to evaluate for disc herniation at L5-S1 (a reported cause of isolated coccydynia without back pain) 5, 6
• Immediate MRI only if red flags are present, particularly for suspected cauda equina syndrome 4

Management Algorithm

First-Line Conservative Therapy (Initial 6 Weeks)

Start with these interventions, as conservative treatment is successful in 90% of coccydynia cases: 3

1. Activity modification and ergonomic adaptations:

   • Use a coccyx cushion (donut or wedge-shaped) to reduce pressure when sitting 2, 3
   • Avoid prolonged sitting; stand and move frequently 5
   • Continue the prone extension position that relieves your pain (McKenzie-type exercises) 1

2. Pharmacologic management:

   • NSAIDs as first-line therapy (lowest effective dose for shortest duration) 5, 1
   • Consider skeletal muscle relaxants if muscle spasm is present 5
   • Avoid opioids unless all other treatments have failed 5

3. Physical therapy:

   • Manual therapy including massage and stretching of levator ani muscle 2
   • Mobilization of the coccyx 2, 7
   • Supervised exercise therapy with stretching and strengthening after 2-6 weeks 1

Second-Line Interventions (After 6 Weeks of Failed Conservative Therapy)

If symptoms persist or worsen despite conservative management:

1. Diagnostic and therapeutic injections:

   • Local anesthetic injection into sacrococcygeal or intercoccygeal discs to confirm coccygeal origin of pain 2
   • Corticosteroid injections into painful structures if diagnostic block is positive 2, 8
   • Consider ganglion impar block for refractory cases 8

2. Advanced interventional techniques:

   • Pulsed radiofrequency ablation of coccygeal discs and Walther's ganglion 2, 8
   • Manual manipulation of the coccyx under anesthesia 7
   • Extracorporeal shock wave therapy 8

3. If lumbar disc herniation is identified:

   • Discoblock (diagnostic disc injection) at L5-S1 to confirm disc as pain source 6
   • Percutaneous discectomy has been effective for coccydynia caused by lumbar disc herniation without back pain 6
   • Epidural steroid injections for radicular symptoms 7

Surgical Consideration (Last Resort)

Coccygectomy (partial or total) is indicated only for refractory cases after failed conservative and interventional therapies:

• Best outcomes occur in patients with documented abnormal coccygeal mobility and bony spicules 2
• Growing evidence supports coccygectomy as effective for debilitating pain unresponsive to other treatments 8
• Reserve for patients who have failed at least 6-12 months of comprehensive conservative management 2, 3

Critical Pitfalls to Avoid

1. Missing lumbar disc herniation as the cause: Coccydynia can be the sole presenting symptom of L5-S1 disc herniation without back pain or sciatica 6

2. Assuming all coccyx pain is coccygeal in origin: In 30% of cases, the cause cannot be found (idiopathic), and extracoccygeal disorders (pilonidal cyst, perianal abscess, pelvic organ disease, sacroiliac joint dysfunction) must be excluded 2

3. Premature surgical referral: 90% of cases resolve with conservative treatment; exhaust non-surgical options first 3

4. Inadequate diagnostic workup: Without dynamic radiographs or diagnostic injections, the specific pain generator cannot be identified, leading to ineffective treatment 2

Recommended Next Steps for Your Specific Case

Given your unique positional pattern (relief with standing and prone extension):

1. Obtain dynamic lateral coccyx radiographs to assess for abnormal mobility 2
2. If radiographs are normal or symptoms persist, obtain MRI lumbar spine to evaluate for L5-S1 disc herniation 6
3. Begin conservative therapy immediately: NSAIDs, coccyx cushion, and continue prone extension exercises that provide relief 5, 1
4. Consider diagnostic injection (discoblock if disc herniation found, or coccygeal injection if abnormal mobility identified) to confirm pain source before proceeding to advanced interventions 2, 6