Neonatal Nurse Practitioner Practice Exam

What characteristic of prematurity is associated with increased popliteal angle?

1. Heel to ear resistance

2. Hip flexion and adduction

3. Decreased muscle tone

4. Hypertonic posture

The correct answer is: Decreased muscle tone

The characteristic of prematurity associated with an increased popliteal angle is decreased muscle tone. In premature infants, the muscle tone is generally lower compared to full-term infants. This hypotonia leads to a more extended posture, particularly evident in the legs. When muscle tone is decreased, the popliteal angle—the angle formed at the back of the knee when the thigh is flexed towards the abdomen—tends to increase, indicating that the infant's legs are less flexed and more extended than would be seen in a full-term infant. Other characteristics that may be present in premature infants, such as heel to ear resistance, hip flexion and adduction, and hypertonic posture, are not typically associated with an increased popliteal angle. Instead, heel to ear resistance would reflect a certain level of muscle tone and flexibility, while hip flexion and adduction are indicative of a typical posture in full-term infants, and hypertonic posture would suggest increased tone, which is contrary to what is observed in premature infants with decreased muscle tone.