Parents should stop their children sitting in the 'W' position as it could cause them a lifetime of pain, experts have warned.
The common way to sit involves the child sitting on their bottom with their knees bent and feet face pointing outwards.
Many kids sit like this when watching TV, but medical professionals are calling on parents to put a stop to it.
According to the Paediatric Therapy Center, children who sit this way after their second birthday may not develop the core strength and balance.
This could impact their ability to jump and run.
It could also leave muscles in their legs, hips and ankles weak and could even cause hip dislocation, reports Women's Health.
London-based osteopath Avni Trivedi has also raised concerns about the position, saying it could cause children a lot of problems in the long run.
She said: "Sitting for too long generally can place undue pressure on the neck, shoulders and upper back.
"For children that may be hypermobile, sitting in the "W" position may overstretch the joints and can weaken the trunk muscles as they are not required to be active."
Instead, parents should encourage their children to sit crossed-legged instead, or sitting with their legs to the side or out in front of them.