Rickets is a term used to describe the histopathological and radiological changes that result from a diverse group of disorders with the final common pathway being the loss of orderly maturation and mineralization of cartilage cells at the growth plate. It is characterized by excessive amounts of undermineralized bone matrix. Simply, it represents osteomalacia in the growing skeleton.

The differential diagnosis for disorders of bone mineralization that result in a rachitic pattern is wide and includes many lesions causing deficiency of calcium or phosphate, the primary components of bone.

Rickets can be associated with the dietary deficiency of vitamin D, needed for absorption of calcium from the gut. Dietary deficiency can result from prematurity, hyperalimentation, prolonged non-supplemented breastfeeding, starvation, or an unusual diet. Dietary rickets usually develops about 3-6 months of age. It ocasionally presents in newborns, especially if they are premature, and is rarely diagnosed in children older than 2 years old. It is common in dark-skinned infants and children who have little exposure to sunlight. Diets low in vitamin D include breast milk from a mother who is a vegetarian, poorly nourished, or takes in little or no milk, eggs, meat, or fish.

The clinical features of rickets include enlarged and distorted bones (bowing), muscle weakness, chest deformities (pectus carinatum and chostochondral thickening), kyphoscoliosis, growth failure, tetany, craniotabes (palpable softening of the cranium), delayed closure of fontanels, and frontal bossing. Laboratory studies will show an increased serum alkaline phosphatase and a decreased calcium-phosphate product.

Radiologic findings of rickets often precede clinical manifestations. Radiologic diagnosis is made by the following findings: widening of the physes, irregular ("frayed") metaphyseal margins, splaying and cupping of the metaphyses, bowing of extremities, and osteopenia.

Radiographs can be limited to the knees and wrists, which are among the areas most affected because they are sites of much linear growth. Widening and lengthening of the growth plate is the earliest radiologic finding of rickets. The irregular metaphyseal margins, with their "frayed" appearance, result from the defective mineralization of the cartilage in the zone of provisional calcification, normally present on the metaphyseal end of the growth plate. Prominence of the rib ends and costal cartilage produces the characteristic rachitic rosary. Defective osteoid mineralization is evident as diffuse osteopenia in the shafts of the long bones. Normal weight-bearing and muscular stresses produce bowing of long bones, manifested as genu valgum or varus.

Other findings can include scoliosis, slipped capital femoral epiphysis, a triradiate configuration of the pelvis, and basilar invagination. A depression along the line of diaphragmatic insertion into the rib cage, known as Harrison's groove, can sometimes be found. In advanced cases, insufficiency fractures (Looser zones)are identified, seen as bilaterally symmetric linear lucencies perpendicular to the cortex.