6 month old began bilateral rhythmic repetitive leg thrusting?

6 month old began bilateral rhythmic repetitive leg thrusting about two weeks ago. Leg thrusts incorporate back arching (imagine a body builder preparing to deadlift a barbell). This can go on for hours!! Distractable. Generally preceded by extreme hyperactivity. More common when tired. Otherwise developing normally. Movement is forceful but smooth – not jerky. No eye roll associated with the movement.
She can run like the wind in her walker but sometime you find her “stuck” in space and time leg thrusting.
I have a few short videos but this site will not allow the upload due to size.
Knee is pulled up to a horizontal position, which if followed by a forceful thrust downward and repeated almost immediately for hours unless distracted. (Both legs move synchronized in this movement)

Medications: None
General Information: Baby takes Zantac for GERD. Baby has not seen a doctor about this.

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2 Answers on "6 month old began bilateral rhythmic repetitive leg thrusting?"

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Dr. Deepak Patel
Dr. Deepak Patel

Hello. It is important that baby’s overall development is ok. If so, baby is probably just developing nervous system and learning use of leg muscles. Should grow out of it . Keep a note of movements and discuss them with your Pediatrician.


It can be myoclonus, chorea etc..

If there are no associated symptoms then probably it is due to just growth of muscular and central nervous system..

But if the symptoms become frequent and continue to worsen you should consult a Paediatrician and get evaluated..

An MRI Scan and a blood test can be done for confirmation..

Hope this helps..