L3 Radiculopathy
This patient has L3 radiculopathy, and the appropriate next step is to obtain lumbar spine MRI without contrast to identify the compressive lesion at the L3 nerve root level. 1
Diagnostic Reasoning
The clinical presentation is pathognomonic for L3 nerve root involvement:
- Dermatomal sensory loss along the medial aspect of the lower leg (just inferior to the knee) is the defining feature of L3 radiculopathy 1
- The pain distribution—buttock, lateral hip, and anterior lateral thigh—follows the L3 dermatome and myotome pattern 1
- This is not hip pathology despite the buttock and lateral hip pain location 1
Key Distinguishing Features
Negative hip-specific tests (FABER and FADIR) effectively exclude intra-articular hip pathology as the primary source, which is critical because the pain location can mislead clinicians toward a hip diagnosis 1. The sensory finding on the medial lower leg is the key differentiator that points to nerve root pathology rather than:
- Hip arthritis (which causes lateral hip/thigh aching without dermatomal sensory loss) 2
- Spinal stenosis (typically bilateral buttocks and posterior leg pain) 2
- Nerve root compression from other levels (different dermatomal patterns) 2
Diagnostic Workup
First-Line Imaging
Lumbar spine MRI without contrast is the first-line imaging study to evaluate for disc herniation, foraminal stenosis, or other compressive pathology at the L3 nerve root level 1. MRI provides superior visualization of nerve root pathology compared to other modalities 1.
Alternative Initial Imaging
Plain radiographs of the lumbar spine (AP and lateral views) may be obtained first if there are concerns about structural abnormalities, but MRI is superior for identifying the actual nerve compression 1.
Important caveat: The absence of a positive straight leg raise test does not exclude upper lumbar radiculopathy (L3-L4), as this test is more sensitive for lower lumbar nerve roots 1.
Treatment Algorithm
Conservative Management First
- Activity modification and physical therapy
- NSAIDs for pain control
- Monitor for 6-12 weeks unless red flags present 1
Interventional Options
Epidural steroid injection under fluoroscopic or CT guidance at the L3 level may provide both diagnostic confirmation and therapeutic benefit if conservative management fails 1.
Surgical Referral Indications
Neurosurgical or spine surgery referral is recommended if:
Critical Pitfall to Avoid
The most common error is misdiagnosing this as hip pathology based solely on the buttock and lateral hip pain location. Always check for dermatomal sensory changes in patients with buttock/hip pain—the medial lower leg sensory loss is the clinical finding that redirects the diagnosis from hip to L3 radiculopathy 1. Ordering hip imaging first would delay appropriate diagnosis and treatment of the actual spinal pathology.