What could be causing shooting pain down my left leg without trauma or swelling, after having upper left leg swelling one month ago, with a normal pelvis X-ray?

Shooting Leg Pain After Prior Swelling: Likely Radiculopathy or Nerve Compression

Your shooting leg pain following prior upper thigh swelling most likely represents lumbar radiculopathy (sciatica) or lumbosacral plexus/sciatic nerve compression, and you need MRI of the lumbar spine as the initial diagnostic study, not repeat pelvic imaging.

Why Your Normal Pelvic X-ray Doesn't Rule Out Serious Pathology

• Radiographs cannot visualize nerve structures, soft tissue masses, or vascular compression—the most common causes of shooting leg pain originating from the pelvis or spine 1.
• Plain X-rays only show bone and are frequently normal in early nerve compression syndromes, even when significant pathology is present 1.
• The temporal relationship between your prior swelling and current shooting pain suggests an evolving process that requires soft tissue imaging 2.

Most Likely Diagnoses Based on Your Presentation

Lumbar Radiculopathy (Sciatica)

• Shooting pain down the leg is the hallmark symptom of nerve root compression, described by patients as rapid movement or expansion of pain from the back/buttock into the leg 3.
• The pain pattern can vary—some experience rapid downward movement, others feel downward expansion of the painful area, and velocity differs between patients 3.
• Prior swelling in the upper thigh could represent referred edema from nerve dysfunction or an unrelated inflammatory process that has since evolved 2.

Lumbosacral Plexus or Sciatic Nerve Compression

• MR neurography detects extraspinal nerve pathology that routine lumbar spine MRI misses—in one study, 13 patients with normal lumbar spine MRI all had diagnostic findings on dedicated nerve imaging 1.
• Causes include fibrous entrapment, muscular entrapment, vascular compression, post-traumatic injury, ischemic neuropathy, or mass lesions compressing the plexus or sciatic nerve 1.
• These conditions frequently present with leg pain and can be associated with swelling from venous compression or inflammation 2, 4.

Iliac Vein Compression Syndrome (May-Thurner Syndrome)

• Present in over 20% of the population and causes left leg pain, swelling, and altered hemodynamics 4.
• While your swelling has resolved, residual nerve irritation from prior venous congestion or persistent subclinical compression could explain ongoing symptoms 4.
• This diagnosis requires vascular imaging (CT or MR venography), not plain radiographs 5.

Recommended Diagnostic Algorithm

Step 1: MRI Lumbar Spine Without and With Contrast

• This is the appropriate initial imaging study for shooting leg pain to evaluate for disc herniation, spinal stenosis, or nerve root compression 1.
• Look specifically for: disc protrusion/extrusion at L4-L5 or L5-S1 levels, foraminal stenosis, or epidural masses 1.

Step 2: If Lumbar MRI is Normal, Obtain MR Neurography of Lumbosacral Plexus

• High-resolution MR neurography with fat-saturated T2-weighted sequences identifies extraspinal nerve pathology that explains symptoms when routine spine imaging is unrevealing 1.
• This study visualizes the lumbosacral plexus and sciatic nerve using anatomic location, fascicular morphology, and signal intensity 1.

Step 3: Consider Vascular Imaging If Nerve Studies Are Normal

• CT or MR venography of the pelvis evaluates for iliac vein compression if there's clinical suspicion based on laterality (left-sided symptoms) and history of swelling 5, 4.
• Duplex ultrasound of the lower extremity can assess for deep venous thrombosis or chronic venous insufficiency 5.

Critical Clinical Pearls

Physical Examination Findings to Document

• Straight leg raise test: Pain radiating below the knee with leg elevation suggests nerve root tension 3.
• Neurologic examination: Test strength (dorsiflexion, plantarflexion), sensation (L4-S1 dermatomes), and reflexes (patellar, Achilles) 6.
• Point tenderness: Palpate the sciatic notch and along the sciatic nerve course to identify focal compression points 1, 6.

Red Flags Requiring Urgent Evaluation

• Progressive motor weakness, saddle anesthesia, or bowel/bladder dysfunction suggest cauda equina syndrome—this requires emergency MRI and surgical consultation 6.
• Fever, elevated inflammatory markers, or systemic symptoms raise concern for infection or inflammatory neuropathy 2.

Common Pitfalls to Avoid

• Do not assume a normal pelvic X-ray excludes significant pathology—nerve compression, vascular abnormalities, and soft tissue masses are invisible on radiographs 1.
• Do not attribute all leg pain to musculoskeletal causes without neurologic evaluation—shooting pain is a neuropathic descriptor that demands assessment of nerve structures 3.
• Do not order CT pelvis as the next study—it provides inferior soft tissue contrast compared to MRI and adds radiation exposure without diagnostic benefit for nerve pathology 5.
• Do not delay imaging if symptoms are progressive—chronic nerve compression can lead to permanent neurologic deficits if not addressed 1, 6.