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My mother has pain over left iliac crest towards the asis on the soft tissues above it as well. Xray shows no significant changes. What can be the differential diagnosis

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differential diagnosis pain over left iliac crest ASIS soft tissue normal xray

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I now have enough information to provide a thorough differential diagnosis. Let me compile this.

Differential Diagnosis: Left Iliac Crest / ASIS Pain with Soft Tissue Involvement, Normal X-Ray

A normal X-ray in this region is actually expected for most soft-tissue and ligamentous causes. Here is a structured differential:

1. Meralgia Paresthetica (Lateral Femoral Cutaneous Nerve Entrapment) - Top Consideration

The lateral femoral cutaneous nerve (L2-L3) exits the pelvis just medial to the ASIS, passing under or through the inguinal ligament. Entrapment here causes:
  • Pain and/or burning, tingling, numbness over the anterolateral thigh
  • Tenderness on palpation medial to the ASIS
  • Positive Tinel sign over the inguinal ligament near the ASIS
  • Often worse with walking/standing, relieved by sitting
  • Associated with obesity, tight belts/waistbands, pregnancy, diabetes
X-ray is normal. Common in middle-aged women. This fits the description of pain over the ASIS and the soft tissues above/around it particularly well. (Rheumatology 2-Volume Set; Gray's Anatomy for Students)

2. Iliac Crest Contusion / "Hip Pointer"

  • Direct trauma to the iliac crest (even minor/forgotten trauma)
  • Point tenderness over the crest and surrounding soft tissue
  • Soft tissue swelling possible
  • X-ray typically normal unless there is an avulsion fracture (which would show up)
  • Managed with ice, compression, pain control (Miller's Review of Orthopaedics)

3. Myofascial Pain Syndrome (Gluteus Medius / Quadratus Lumborum / TFL Trigger Points)

  • Gluteus medius trigger points are found along the entire iliac crest from the ASIS to the sacroiliac joint; they produce pain projecting along the iliac crest into the hip, thigh, and calf
  • Quadratus lumborum trigger points cluster around the iliac crest and the 12th rib, producing local and referred anterior abdominal pain
  • Tensor fascia lata (TFL) / Fascia Lata Syndrome - TFL originates from the ASIS and anterior iliac crest; overuse or injury causes anterior groin pain and point tenderness directly over the anterior iliac crest and ASIS
  • All produce normal X-rays (Roberts and Hedges' Emergency Medicine; Tintinalli's Emergency Medicine)

4. Iliolumbar Ligament Strain / Syndrome

  • The iliolumbar ligament runs from the L5 transverse process to the iliac crest
  • Strain causes persistent low back pain radiating to the iliac crest, hip, and sometimes groin
  • Pain worsens with bending and twisting
  • X-ray is normal
  • Often seen after acute strain or repetitive loading

5. Enthesopathy / Muscle Origin Strain at the Iliac Crest

Multiple muscles originate along the iliac crest and ASIS:
  • Sartorius - originates at ASIS
  • Tensor fascia lata - originates at ASIS and anterior iliac crest
  • Abdominal muscles (external oblique, internal oblique, transversus abdominis) - attach along the iliac crest
  • Strain or enthesopathy at any of these insertion points causes local tenderness with soft tissue involvement; X-ray normal

6. Lateral Hip / Trochanteric Area Bursitis (if pain extends laterally)

  • Though classically over the greater trochanter, a tender iliac crest can sometimes be part of a broader greater trochanteric pain syndrome / abductor enthesopathy complex
  • Normal X-ray; MRI or ultrasound would clarify (Bailey and Love's Surgery)

7. Iliotibial Band Syndrome (if lateral component)

  • The ITB originates from the iliac crest and runs down the lateral thigh
  • Inflammation at the proximal origin can produce iliac crest and anterolateral hip pain
  • Normal X-ray; ultrasound/MRI diagnostic

8. Less Common / Must-Not-Miss

ConditionKey Feature
Avulsion fracture (ASIS or iliac apophysis)Usually in adolescents/young adults; sudden onset with forceful muscle contraction; may be subtle on X-ray - needs CT/MRI
Stress fracture of iliac crestOlder women, osteoporosis, repetitive activity; X-ray often normal early - bone scan or MRI needed
Lumbar radiculopathy (L1-L2)Referred pain to iliac crest and inguinal region; back symptoms often present
Hernia (inguinal/femoral)Pain near ASIS/inguinal region; examine for defect
Lymph node pathologyInguinal lymphadenopathy can cause regional soft tissue pain
Referred pain from SI joint dysfunctionSacroiliac joint pathology commonly refers to the iliac crest and ASIS area
Soft tissue tumour (lipoma, sarcoma)Rare; palpable mass; MRI required

Recommended Next Steps

Given a normal X-ray:
  1. MRI of the pelvis/hip - best for soft tissue, stress fractures, enthesopathy, nerve entrapment
  2. Ultrasound - for bursitis, TFL/fascia lata syndrome, meralgia paresthetica confirmation
  3. Neurological exam - test sensation over the anterolateral thigh (meralgia paresthetica pattern)
  4. Tinel test at ASIS/inguinal ligament - if positive, strongly suggests lateral femoral cutaneous nerve entrapment
  5. Age consideration - if your mother is older, stress fracture and osteoporosis-related pathology should be higher on the list
The most common diagnosis in this anatomical location with a normal X-ray in a woman is either meralgia paresthetica (nerve entrapment) or myofascial pain involving the gluteus medius, TFL, or iliac crest muscle attachments.

No recent trauma

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Good - I now have enough to give a refined, atraumatic-focused differential. Here is the updated list:

Refined Differential - Atraumatic Left Iliac Crest / ASIS Pain, Soft Tissue Involvement, Normal X-Ray

With no trauma, the list narrows to degenerative, neurogenic, myofascial, inflammatory, and referred causes. Ranked by likelihood:

1. Meralgia Paresthetica (Lateral Femoral Cutaneous Nerve Entrapment) - Most Likely

The lateral femoral cutaneous nerve (L2-L3) passes under the inguinal ligament just medial to the ASIS - the most common site of spontaneous entrapment. It does NOT require trauma.
Atraumatic causes include:
  • Obesity (most common)
  • Tight waistbands, belts, or clothing
  • Pregnancy or recent weight gain
  • Diabetes mellitus
  • Prolonged sitting/standing postures
  • Aging and ligamentous laxity
What you would find: Burning/aching pain and/or numbness at the ASIS and along the anterolateral thigh. Tinel sign medial to the ASIS. Symptoms worse with standing and walking, better with sitting. X-ray completely normal. (Rheumatology 2-Vol Set; Harrison's Principles of Internal Medicine 22E)

2. Myofascial Pain Syndrome

Three muscle groups insert along the iliac crest and ASIS and develop trigger points without trauma:
  • Tensor Fascia Lata (TFL) - originates at ASIS and anterior iliac crest; overuse (even from prolonged sitting or gait imbalance) causes anterior iliac crest pain and point tenderness directly over the ASIS area
  • Gluteus Medius - trigger points run the full length of the iliac crest from ASIS to the SI joint; common cause of iliac crest pain that mimics other conditions; often bilateral or unilateral without any injury
  • Quadratus Lumborum - trigger points cluster around the iliac crest and cause local pain plus referred anterior abdominal wall pain
All three produce normal X-rays. Diagnosis is by palpation for trigger points. (Roberts and Hedges' Emergency Medicine)

3. Sacroiliac Joint Dysfunction

The SI joint has wide segmental innervation (L2-S2), so its referral pattern is variable. The most consistent referral zone is just inferior to the posterior superior iliac spine, but pain commonly extends forward toward the ASIS and iliac crest on the same side.
Atraumatic causes:
  • Degenerative joint disease / osteoarthritis of the SI joint
  • Inflammatory arthritis (ankylosing spondylitis, psoriatic arthritis, reactive arthritis)
  • Pregnancy-related ligamentous laxity
  • Leg length discrepancy causing asymmetric loading
X-ray is often normal early; SI joint sclerosis or erosion may be seen later. (Campbell's Operative Orthopaedics 15th Ed)

4. Iliolumbar Ligament Syndrome

The iliolumbar ligament connects the L5 transverse process to the posterior iliac crest. Chronic postural strain - not acute trauma - is the most common cause. The pain is felt along the iliac crest and can radiate to the groin and anterior thigh.
Triggers: prolonged sitting, forward flexion postures, lumbar spondylosis, hyperlordosis. X-ray normal.

5. Lumbar Referred Pain (L1-L2-L3 Radiculopathy or Nerve Root Irritation)

The upper lumbar nerve roots refer pain to the iliac crest, inguinal region, and anterior thigh. Lumbar disc disease or facet joint arthropathy at L1-L2 or L2-L3 can produce pain felt entirely in the iliac crest/ASIS region with no back pain at all in some patients. X-ray of the pelvis would be normal; lumbar X-ray or MRI would be the relevant investigation.

6. Insertional Tendinopathy / Enthesopathy

Degenerative changes at the muscle-bone insertion points along the iliac crest (sartorius at ASIS, external oblique/internal oblique along the crest) cause chronic pain without trauma. More common with aging. Normal X-ray; ultrasound or MRI shows tendon thickening or calcification.

7. Stress Fracture of the Iliac Crest

Even without acute trauma, insufficiency stress fractures can occur in:
  • Osteoporotic older women
  • Women on long-term steroids
  • Those with recent increase in walking/activity
Critically, X-ray is often NORMAL in early stress fractures - bone scan or MRI is needed. This must not be missed.

8. Inflammatory / Rheumatological

  • Seronegative spondyloarthropathies (ankylosing spondylitis, psoriatic arthritis) - can cause enthesitis at the iliac crest; morning stiffness, responds to NSAIDs
  • Crystal arthropathy (gout, calcium pyrophosphate) - can affect soft tissues around the iliac crest
  • Fibromyalgia - iliac crest is a recognised tender point location

9. Abdominal / Pelvic Referred Pain

Pain originating in the left lower quadrant can be felt over the left iliac crest:
  • Diverticular disease (very common in older women, left-sided)
  • Ovarian pathology (cyst, endometrioma) - if premenopausal or perimenopausal
  • Psoas abscess or haematoma - rare but presents as hip/iliac fossa pain
  • Inguinal/femoral hernia at the level of the ASIS

Prioritised Investigation Plan

TestTargets
MRI pelvis/hipStress fracture, enthesopathy, SI joint, TFL, gluteus medius, nerve
Lumbar spine MRIL1-L3 radiculopathy, disc disease
Ultrasound (hip/pelvis)Bursitis, tendinopathy, soft tissue mass
Nerve conduction studyConfirm meralgia paresthetica
Blood tests (ESR, CRP, HLA-B27, RF, uric acid)Inflammatory/rheumatological causes
Abdominal/pelvic ultrasoundRule out visceral referred pain

Bottom Line

In an atraumatic presentation in a woman, the top three diagnoses to pursue are:
  1. Meralgia paresthetica - check for burning quality, anterolateral thigh numbness, Tinel at ASIS
  2. Myofascial pain (TFL / gluteus medius trigger points) - check for trigger points on palpation
  3. Referred pain from SI joint or lumbar spine - check lumbar movements and SI joint provocation tests
An MRI of the hip and pelvis would be the single most informative next step.
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