A common complaint from children is growing pains: a mild to severe pain located primarily in the legs and being most intense in evenings and during sleep. The diagnosis is based on the characteristics of the pain and careful clinical examination. The pain disappears as the child grows up. Research has suggested that the pain occurs more often in children who suffer from vitamin D deficiency, low bone density, low pain threshold, restless legs syndrome and in children who were breastfed for less than 40 days from birth. There are not yet any firm conclusions about the aetiology.