This maneuver assesses maturation of passive flexor tone about the knee joint by testing for resistance to extension of the lower extremity.
Term newborns are less flexible, with about a 90-degree angle. With very preterm newborns, the leg straightens to a 180-degree angle.
How to Examine Popliteal Angle of the Infant
With the infant lying supine, and with diaper re-moved, the thigh is placed gently on the infant's abdomen with the knee fully flexed. After the infant has relaxed into this position, the examiner gently grasps the foot at the sides with one hand while supporting the side of the thigh with the other.
Care is taken not to exert pressure on the hamstrings, as this may interfere with their function. The leg is extended until a definite resistance to extension is appreciated. In some infants, hamstring contraction may be visualized during this maneuver. At this point the angle formed at the knee by the upper and lower leg is measured.
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SIGN
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NEURO-MUSCULAR MATURITY SCORE
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SIGN SCORE
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-1
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0
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1
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2
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3
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4
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5
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Popliteal Angle
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Note: a) It is important that the examiner wait until the infant stops kicking actively before extending the leg. b) The prenatal frank breech position will interfere with this maneuver for the first 24 to 48 hours of age due to prolonged intrauterine flexor fatigue. The test should be repeated once recovery has occurred; alternately, a score similar to those obtained for other items in the exam may be assigned.