The phenomenon of the anatomical short leg can occur for many reasons and throughout the childs growth cycle and can lead to; overuse injuries, a variety of joint problems through the hip, knee, and ankle related to asymmetry, meniscal tears, herniated disc, back pain, etc..
An experienced professional should be able to identify leg length discrepancy through observation while the child is standing and should include a quick examination of the feet. Measures of functional leg length are NOT the same thing. There are many reasons why there could be a functional leg length deficit while lying down; muscular injury and contraction and back problems being the most likely. There are also problems in the feet such as a pronation "flat foot" or ankle rotation that could be false indicators of a short leg.
So how do you tell if your child may have a short leg? Well, we noticed in our own child when his tummy started protruding slightly and his body began to shift to the left. His left foot also began to splay out and the arch to drop slightly toward the ground. Did we rush to get him a heel lift? Of course not, physician heal thyself is a common saying for a reason. The condition continued and his shift became more pronounced, the left shoulder began to shift up compared to the right and the tummy protruded even more. His posture began to look very similar to this, but in the picture the left shoulder has not begun to shift up, a more chronic sign.
Guess what. It works! And it worked for our son, thus the one moment of being an unequivocally good mom. Over a period of six months, through two growth spurts, he went from having marked postural problems and foot pronation with accompanying motor dysfunction (mild clumsiness), to being perfectly balanced. All we did was give him orthotics for both feet to support the arches and under the orthotic, a heel lift on the short leg side. We did not equalize the legs with the heel lift but actually went higher to cause the weight to shift to the long leg side. And upon normalizing the posture, which we look for in follow-up appointments, we stopped the intervention. The most important part!