Copyright 2009
Definition
Rickets of the knee is an osteomalacic syndrome in which there is an inability to mineralize chondroid and osteoid. There exists a lack of available calcium or phosphorus (or both) for mineralization of newly formed osteoid. Osseous changes in both adults and children reflect that either ionized Ca or phos, or both, is insufficient in concentration to mineralize the skeleton fully.
Rickets is characterized by osseous changes in the rapidly growing skeleton with resulting bowing deformities in the extremities and particularly about the knee. Children can have brittle bones, physeal cupping and widening, bowing of long bones, transverse radiolucent (Looser’s) lines, ligamentous laxity, flattening of skull, enlargment of the costal cartilages (rachitic rosary), and dorsal kyphosis of the spine.
It can be caused by numerous factors including vitamin deficiency secondary to poor diet or decreased sunlight. Since vitamin D is common in US childrens diets secondary to fortification, this is a less common cause in the US. Gastrointestinal malabsorption, renal malresorption, hypophosphatemia, and certain medications can all be factors in the disease.
Diagnosis is suspected clinically by history and physical. Labwork can confirm deficiency states and x-rays have a very typical appearance (see above) that will confirm the diagnosis.
Imaging includes the use of plain x-rays. MRIs are not necessary in diagnosing or treating the disease.
Treatment options always include treating the underlying cause of the rickets. Surgical intervention is rarely needed.
References
http://www.wheelessonline.com/ortho/rickets