What are the typical symptoms and presentation of L4 (Lumbar 4) lumbar radiculopathy?

L4 Lumbar Radiculopathy: Clinical Presentation

L4 radiculopathy presents with pain radiating down the anterior and medial thigh to the medial lower leg, accompanied by weakness of knee extension, diminished patellar reflex, and sensory loss over the medial leg and foot.

Pain Distribution and Character

• Radicular pain follows the L4 dermatome, typically radiating from the lower back through the anterior and medial thigh to the medial aspect of the lower leg and foot 1, 2
• The pain has a neuropathic character with dysesthesia, burning, or electric sensations that distinguish it from mechanical back pain 1
• Pain intensity can range from mild to severe, with some patients experiencing periodic tingling sensations in the affected distribution 2

Motor Deficits

• Weakness of knee extension is the hallmark motor finding, as the L4 nerve root innervates the quadriceps muscle 3
• Diminished knee strength on examination is characteristic and helps localize the lesion to L4 1
• Motor deficits may be subtle in early or mild cases but become more pronounced with progressive nerve root compression 3

Reflex Changes

• Diminished or absent patellar (knee jerk) reflex is the primary reflex abnormality, as this reflex is mediated by the L3-L4 nerve roots 1, 3
• The patellar reflex should be tested bilaterally for comparison, as asymmetry is more clinically significant than bilateral changes 3

Sensory Abnormalities

• Sensory loss or paresthesias occur over the medial leg and medial aspect of the foot, following the L4 dermatome distribution 2, 3
• Patients may report numbness, tingling, or altered sensation in this distribution 2
• Sensory deficits may be patchy or incomplete, particularly in early presentations 4

Physical Examination Findings

• Straight leg raise test may be positive, though it is more sensitive for lower lumbar radiculopathies (L5-S1) than L4 1, 4
• Proprioception deficits in the affected leg can occur, potentially causing balance problems 2
• A positive Romberg test may be present when proprioceptive deficits are significant 2

Clinical Pitfalls and Caveats

• Individual clinical tests have low diagnostic accuracy when used in isolation, with positive likelihood ratios typically <4.0 for detecting nerve root impingement 4
• The overall clinical evaluation combining multiple findings is more accurate than individual tests, with a positive likelihood ratio of 6.28 for L4 nerve root impingement 4
• Imaging findings do not always correlate with symptoms, as disc abnormalities are common in asymptomatic patients 1
• L4 radiculopathy is less common than L5 or S1 radiculopathy, as most symptomatic lumbar disc herniations occur at L4-L5 and L5-S1 levels 1
• Extraforaminal disc herniation is a rare but important cause of L4 radiculopathy that may be missed on routine imaging 2

Diagnostic Confirmation

• MRI is the preferred imaging modality for confirming nerve root compression when patients fail conservative management or are surgical candidates 1
• Electrodiagnostic studies should be used to confirm the clinical diagnosis and differentiate radiculopathy from plexopathy or peripheral nerve lesions 1, 5
• Imaging should be reserved for patients with persistent symptoms after 6 weeks of conservative therapy who are candidates for surgery or intervention 1