W-sitting in often used in children to compensate for decreased trunk strength by widening their base of support. This position does not challenge their sitting balance and trunk strength to develop core stability.
Decreased Crossing Over Midline:
W-sitting discourages full trunk rotation and crossing over midline with their arms (or the ability to shift their weight from side to side). This delay of crossing over midline can also postpone the child developing a hand preference since objects on left are picked up by the left hand and objects on the right are picked up by the right hand.
W-sitting may decrease flexibility in a child’s hamstrings, hip abductors, internal rotators and heel cords (muscles of the hip, thigh and calf) by placing these structures in an extremely shortened range.
W-sitting may predispose a child to hip dislocation (the hip slipping out of the socket that holds the leg to the pelvis). A research study using MRI has shown that during w-sitting all participants experienced hip subluxation (slipping of the 2 hip bones out of place). 1 Another study showed that habitual w-sitting may also lead to excessive lateral tibial torsion (the thigh bone rotating permanently out of line with the hip socket).2
- Yamamura, M. et al. “An open-configuration MRI study of the femoro-acetabular impingement and subluxation in extreme leg position.” International Congress Series 1268 (2004): 597-601.
- Magee, David J. Orthopedic Physical Assessment> Philadelphia: W. B. Saunders Company, 1997.