Sacral Region Pain - Only on Deep/Hard Touch

Anatomy Map - What You Are Pressing On

• Adams and Victor's Principles of Neurology, 12th Ed., Fig. 10-2, p. 218

Differential Diagnosis

• Most common in elderly women with osteoporosis, or after radiation therapy
• Presents as low back/sacral pain that is present at rest but markedly worsened by direct pressure or percussion over the sacrum
• Often bilateral, H-shaped pattern on bone scan ("Honda sign")
• MRI or bone scan is far more sensitive than plain X-ray
• Grainger & Allison's Diagnostic Radiology describes sacral insufficiency fractures as a well-recognized complication of generalized osteoporosis, visible on MRI as bilateral signal changes flanking the sacral ala

• Pain typically at or below the posterior superior iliac spine (PSIS)
• Tenderness on direct pressure over the SI joint/sulcus is a cardinal sign
• SI joint pain accounts for 15-30% of chronic low back pain cases
• Provocation tests (FABER/Patrick, Gaenslen's, compression/distraction) help confirm
• Etiologies: osteoarthritis, seronegative spondyloarthropathy (ankylosing spondylitis, psoriatic arthritis), infection, pregnancy-related
• Adams and Victor: "In cases of sacroiliac joint disease, abduction of the upside leg against resistance reproduces pain in the sacroiliac region" (p. 218)

• Tenderness over the interspinous ligaments or articular facets between L5 and S1 is consistent with lumbosacral disc disease
• May be accompanied by radiation to the leg (S1 root: posterior calf, heel, lateral foot)
• Adams and Victor, p. 218: "Tenderness over the interspinous ligaments or over the region of the articular facets between the fifth lumbar and first sacral vertebrae is consistent with lumbosacral disc disease"

• Pain specifically at the sacrococcygeal junction on firm pressure
• Occurs notably on sitting; patient shifts from buttock to buttock
• Caused by fall onto coccyx, prolonged sitting, or childbirth trauma
• Goldman-Cecil Medicine: "Coccydynia is manifested by pain in the coccyx area when pressure is applied to the area. This most notably occurs on sitting."

• Localized deep bone tenderness on percussion is a classic sign of bone infiltration
• Adams and Victor (p. 218): "Localized tenderness is seldom pronounced in disease of the spine because the involved structures are so deep, but there are exceptions - tumor in the spinal bones and epidural abscess, and pathologic or traumatic compression fracture"
• Red flags: age >50, prior malignancy, unexplained weight loss, night pain
• Workup: ALP, PSA (prostate), serum protein electrophoresis (myeloma), Ca2+, MRI

• Rare but serious; deep percussion tenderness + fever, elevated ESR/CRP
• Risk factors: IV drug use, immunosuppression, recent spinal procedure

• After trauma or pregnancy; tenderness over the SI ligaments (between PSIS and PIIS)
• Pain with SI provocation maneuvers

• Uterine, rectal, or pelvic organ pathology can refer to the sacral area
• However, referred pain typically does NOT produce focal bony point tenderness
• Firestein & Kelley's Textbook of Rheumatology: "visceral pain radiates to the sacral area from lower abdominal diseases"

Key Clinical Clues

Suggested Workup

1. History: Age, onset, trauma, constitutional symptoms, posture-related vs. constant
2. Examination: Localize the exact point of tenderness (see figure above); provocative SI joint tests; neurological exam of lower limbs
3. Imaging:
   • X-ray sacrum/pelvis: first step (fractures, spondyloarthropathy)
   • MRI pelvis/sacrum: best for soft tissue, stress fracture, infection, tumor
   • Bone scan: if insufficiency fracture suspected and MRI unavailable
4. Labs (if red flags): CBC, ESR, CRP, ALP, calcium, PSA, SPEP, HLA-B27

Note: The fact that pain is present only on hard touch and absent at rest is reassuring against acute fracture (which usually hurts constantly) and more consistent with SI joint dysfunction, ligamentous pathology, or an early/chronic bone lesion. However, sacral insufficiency fractures in the elderly can sometimes be surprisingly mild at rest.

Assessment: Under 30, Minor/Indirect Trauma, No Other Symptoms

• Young age - rules out insufficiency fracture, malignancy, degenerative disease
• Minor/indirect trauma - the most common cause of localized sacral tenderness in young people is a direct contusion or sprain of the sacrococcygeal ligaments/periosteum
• Pain only on hard touch, absent at rest - this "deep tenderness only" pattern is classic for a bone contusion or periosteal bruise, where the injury is sub-threshold at rest but the nerve endings in the periosteum respond sharply to mechanical pressure
• No radiation, no stiffness, no fever - makes disc disease, sacroiliitis, and infection very unlikely

What Likely Happened

What You Can Do

1. Avoid direct pressure - use a coccyx/donut-shaped cushion when sitting
2. NSAIDs (e.g., ibuprofen 400 mg with food) for 5-7 days to reduce periosteal inflammation
3. Cold pack for first 48 hours, then warm compresses
4. Avoid activities that reproduce the pain (prolonged sitting on hard surfaces, impact sports)

When to Seek Medical Review

• Pain starts occurring at rest or at night
• Pain worsens over 2 weeks instead of improving
• You develop numbness, tingling, or weakness in the legs
• Fever or chills appear (rules out infection)
• The mechanism of injury was more forceful than initially recalled (rules out fracture)