By supplying an adequate amount of calcium and vitamin D with the addition of weekly bisphosphonate, the investigators will be able to increase bone mass and decrease the incidence of fragility fractures in these children with muscular dystrophy.

The investigators think this treatment will also decrease the intensity of pain frequently present in these patients and slow the progression of scoliosis.

Children with muscular dystrophy, as well as children with other chronic diseases (e.g. cystic fibrosis, chronic inflammatory arthritis) are at risk to develop fragility fractures both due to the disease itself and to drugs (mostly corticosteroids) used to treat the diseases.

In addition, children with muscular dystrophy frequently complain of diffuse pain making daily care more difficult and almost always develop structural scoliosis.

The objective of the present protocol is to offer these children a preventive treatment aimed at maintaining or increasing their bone mass. We also propose that maintaining bone mass will decrease fracture rates, as well as pain and the rate of progression of scoliosis.

Rigorous care to ensure adequate intake of calcium and vitamin D, as well as addition of a weekly bisphosphonate, are the central aspect of the project. In addition, we will monitor to avoid possible side-effects such as hypercalciuria and kidney stones.

Inclusion Criteria:

• Osteoporosis or osteopenia
• Severe muscular dystrophy or cystic fibrosis
• May use corticosteroids

Exclusion Criteria:

• Inability to consent or to take drugs by mouth