Test: Prone Knee Bending Test

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Background/Purpose

The Prone Knee Bending Test, also known as the Femoral Nerve Stretch Test, Nachlas Test, or Ely's Test (though technically Ely's Test has different criteria), is a neurodynamic assessment used to evaluate tension or irritation of the femoral nerve and its nerve roots (L2, L3, L4). This test is designed to identify femoral nerve pathology, upper lumbar nerve root compression, or irritation of the neural structures in the anterior thigh. The femoral nerve can become compromised due to lumbar disc herniation (particularly at L3-L4), lumbar stenosis, diabetic neuropathy, psoas muscle dysfunction, or direct trauma. The test increases tension on the femoral nerve by combining hip extension with knee flexion, which stretches the nerve along its anatomical course. It is commonly used in patients presenting with anterior thigh pain, radiating pain into the anterior or medial leg, or suspected upper lumbar radiculopathy. The test helps differentiate neural causes of anterior thigh pain from musculoskeletal conditions such as rectus femoris tightness or hip flexor contractures.

Procedure

Patient Position:
The patient lies prone (face down) on the examination table
The head can be turned to either side for comfort
Arms should be positioned comfortably at the sides or with hands under the forehead
Both legs are initially extended and relaxed in neutral position
A pillow may be placed under the abdomen if needed for patient comfort

Procedure:
Stabilization: Stand on the side of the leg being tested. Place one hand on the patient's buttock/sacral region to stabilize the pelvis and prevent compensation through lumbar extension or pelvic rotation
Passive Knee Flexion: With your other hand, grasp the patient's ankle and passively flex the knee, bringing the heel toward the buttock
Progressive Flexion: Continue to flex the knee slowly and progressively until:

The heel contacts or nearly contacts the buttock
The patient reports symptom reproduction
Resistance is felt
The pelvis begins to rotate or lift off the table

Hip Extension (Optional Sensitizing Component): If knee flexion alone does not reproduce symptoms, you may add hip extension by gently lifting the thigh off the table while maintaining knee flexion. This further increases tension on the femoral nerve
Observation: Monitor for:

Symptom reproduction (location, quality, intensity)
Compensatory movements (lumbar extension, pelvic rotation, hip hiking)
Range of motion achieved
The patient's pain response

Comparison: Repeat the test on the opposite leg for comparison
Differentiation: To differentiate neural symptoms from rectus femoris tightness, symptoms that radiate into the anterior thigh, groin, or lumbar spine suggest neural involvement, while isolated anterior thigh tightness without radiating pain suggests muscular restriction

Important Notes:
Maintain pelvic stabilization throughout to ensure accurate assessment
The test should be performed slowly to avoid muscle guarding
Document the exact location and nature of symptoms
Performed: Unilaterally

Dialog

The patient lies prone while the examiner passively flexes the knee, bringing the heel toward the buttock to tension the femoral nerve and assess for nerve root irritation or femoral nerve pathology.

Criteria

• No radicular symptoms
• No asymmetrical response of neural quality
• more than 130 degrees of knee flexion

Measurement

LOINC Code

Scale/Grading

selection range; grade - LOINC ID
Option - Value option selection range; grade - LOINC IDPass ; Pass - Fail ; Fail -