Many children immediately assume the W sitting position to play, and maintain it for a considerable period of time, without any attempts to transition into a new position.
Why do children W-sit? Every child needs to play and children don’t want to worry about keeping their balance when they’re so much focused on a playing. Children who frequently assume a W-sitting position often rely on this position to gain more trunk and hip stability which allows easier toy manipulation and play.
When in the W-position, a child is planted in place or "fixed" through the trunk. This allows for play with toys in front, but does not permit trunk rotation and lateral weight shifts (twisting and turning to reach toys on either side). Trunk rotation and weight shifts over one side are necessary for crossing the midline while writing and doing table top activities; additionally, they allow a child to maintain balance while running outside or playing on the playground.
The problem is that continued reliance on W-sitting can prevent a child from developing more mature movement patterns necessary for higher-level skills. When playing in other sitting postures, children have the ability to develop the trunk control and rotation necessary for midline crossing (reaching across the body) and separation of the two sides of the body. These skills are needed for a child to develop refined motor skills and hand dominance.
So, what’s wrong with W sitting?
Biomechanics and orthopedic concerns: W-sitting requires the hips to be positioned in extreme internal rotation – way past what is functional. This leads to long term problems with the hips and knees. Major muscle groups become very tight, causing in-toeing during gait. Kids who chronically w-sit have more shallow hip sockets, which can prove to be problematic with prolonged exposure. W-sitting is also hard on the knee joint as this position causes excessive valgus (i.e. bad) forces on the joint. Developmentally, a child who w-sits often has a weak core (the muscles in their trunk are weak). W-sitting puts strain on their ligaments for stability, and is bad for their joints. W-sitting can also discourage a child from developing a hand preference. Because no trunk rotation can take place when W-sitting, a child is less inclined to reach across the body and instead picks up objects on the right with the right hand, and those placed to the left with the left hand. This causes impaired functional postural control, balance, and pelvic stability. It can also cause problems with the development of fine motor skills and coordination, like tying their shoe lace. Sitting in this position predisposes a child to stand and walk in this position (knock kneed and pigeon toed), which is not only awkward looking, but also biomechanically inefficient.
How to prevent W-sitting?
The most effective and practical means to prevent W-sitting is to prevent it from becoming a habit from the get go. Children should be supervised and instructed to assume alternative sitting positions. If a child discovers W-sitting anyway, help him/her to move to another sitting position, or say, "Fix your legs." Consistency is necessary. When playing with a child on the floor, hold his/her knees and feet together when kneeling or creeping on hands and knees, this will make it impossible to get into a W-position. The child will either sit to one side, or sit back on his/her feet; he can then be helped to sit over to one side from there (try to encourage sitting over both the right and left sides). If a child is unable to sit alone in any position other than a W, a therapist may be consulted.