Diagnosis: L3 Radiculopathy
This patient has L3 radiculopathy, not primary hip pathology, based on the characteristic diminished sensation along the medial right lower leg (L3 dermatome distribution) and asymmetric patellar reflexes. 1
Clinical Reasoning
The key diagnostic features that distinguish this from hip pathology include:
Dermatomal sensory loss: The diminished sensation along the medial aspect of the right lower leg just inferior to the knee corresponds precisely to the L3 dermatome distribution, which is pathognomonic for L3 nerve root involvement 1
Asymmetric deep tendon reflexes: The 1+ patellar reflex on the right compared to 3+ on the left indicates L3-L4 nerve root dysfunction, as the patellar reflex is mediated by these nerve roots 1
Negative hip-specific tests: The negative FABER and FADIR tests effectively exclude intra-articular hip pathology as the primary source of pain 1, 2
Negative straight leg raise: While this test is more sensitive for lower lumbar radiculopathy (L5-S1), its absence doesn't exclude upper lumbar radiculopathy (L3-L4) 1
Diagnostic Pitfall to Avoid
Hip pain is frequently referred from the lumbar spine, and this is a common diagnostic error. 1, 3 The ACR guidelines specifically emphasize that spine imaging should be considered for referred pain when hip-specific examination findings are negative 1. Many clinicians mistakenly focus on the hip when the neurologic examination clearly localizes to a spinal nerve root 1.
Recommended Diagnostic Workup
Initial Imaging
Obtain lumbar spine MRI without contrast as the first-line imaging study to evaluate for disc herniation, foraminal stenosis, or other compressive pathology at the L3 nerve root level 1
Plain radiographs of the lumbar spine (AP and lateral views) may be obtained first if there are concerns about structural abnormalities, but MRI provides superior visualization of nerve root pathology 1
Secondary Considerations
- Hip radiographs (AP pelvis and frog-leg lateral) are reasonable to obtain if there is diagnostic uncertainty, but the neurologic findings strongly suggest radiculopathy rather than hip joint pathology 1, 2
Treatment Approach
Conservative Management (First-Line)
Physical therapy focused on lumbar stabilization and nerve root decompression exercises 4, 3
Avoid prolonged bed rest; encourage activity modification 3
Advanced Interventions if Conservative Management Fails
Epidural steroid injection under fluoroscopic or CT guidance at the L3 level may provide diagnostic confirmation and therapeutic benefit 1
Neurosurgical or spine surgery referral if there is progressive neurologic deficit or failure of conservative management after 6-12 weeks 1
Why This Is NOT Hip Pathology
The clinical presentation argues strongly against primary hip disorders:
Osteoarthritis: Would present with groin pain, positive FABER test, and no dermatomal sensory loss 1, 3, 5
Greater trochanteric pain syndrome: Would cause lateral hip pain with tenderness over the greater trochanter, not medial leg sensory changes 6, 4, 7
Labral tear or FAI: Would cause anterior groin pain with positive FADIR test and mechanical symptoms like catching or locking 1, 2, 3
Intra-articular pathology: Would be relieved by intra-articular anesthetic injection, but the dermatomal pattern and reflex asymmetry cannot be explained by hip joint disease 1, 2