W-sitting is a normal developmental position that babies usually discover when they sit back straight from their hands and knees. Their legs will then form a “W.” Often, babies also transition back to a single hip, toward a side sitting position. When a baby varies his or her sitting position, W-sitting is rarely a problem.
However, when a baby sits back straight to a W-sit consistently, they don’t get the opportunity to elongate and activate lateral trunk muscles to develop their core muscles. W-sitting is a very stable position that children find useful, however, it allows them to play without developing muscle that provide the ability for kids to reach out to their sides or rotate across their midline, leading to underdevelopment of lower trunk muscles, which stabilize the pelvis.
When a child uses this position as their preference without the normal variety in movements, it can affect development. They may demonstrate an in-toeing gait, core weakness or balance difficulties. The hips are positioned in extreme internal rotation, placing stress on the hips and the knee joints. This can lead to hip and knee orthopedic issues as the child develops.
So, what can you do to prevent any development issues? Encourage your child to alternate sitting positions, such as side sitting (alternating sides), ring sitting, or, with older children, sitting in a chair or on a ball. This might be challenging initially, but once your child gets used to it, they may just need reminders.
If it’s difficult for your child to sit in alternate positions or they begin to show other developmental concerns, a referral to a physical therapist may be helpful to facilitate trunk muscle development.
Eileen McMahon, M.S.P.T., is a physical therapist at MidMichigan Health.