What maneuvers on physical exam suggest lumbar spine nerve root irritation?
• Femoral nerve stretch test: this test is performed to evaluate the upper lumbar roots (L2 to L4). With the patient prone, the examiner maximally flexes the knee (80–100 degrees). If no symptoms, then the hip is gently extended (examiner lifts the thigh off table). Anterior thigh (L2, L3) or medial leg (L4) pain is suggestive of a lumbar root lesion. Ipsilateral quadriceps tightness or significant hip pathology may reduce specificity. Testing of the contralateral side is recommended; sensitivity and specificity 88%.
• Straight-leg raise (Lasegue’s sign): evaluates the sciatic nerve roots (L4 to S1) and is performed with the patient supine. The examiner passively raises the extended leg, by the foot, to 70 degrees of elevation. Dermatome pain radiating below the knee upon raising the leg between 30 degrees and 70 degrees of elevation is a positive test for nerve root irritation. A positive test is more convincing if passive ankle dorsiflexion reproduces the pain after the leg has been lowered to an angle that abolished the radicular pain; sensitivity 52% to 71% and specificity 47% to 66%.
• Crossed-straight leg test: this test causes contralateral radiating pain when the unaffected leg is elevated. It is usually seen in patients with a herniated disc and is more specific but less sensitive than the straight-leg raise test; sensitivity 28% to 43% and specificity 83% to 88%.
• Slump test: the patient sits with the head bent forward and leg outstretched, toes pointing upwards. The examiner gently eases the patient forward to increase the stretch on the sciatic nerve; sensitivity 44% to 87% and specificity 23% to 63%.
