Patient is between ages 4 and 18 at the time of study Patients must be of Black, White or Hispanic descent Patient has sustained a 30% or greater total body surface area burn Patient is enrolled ≤ 21 days of admission to the acute unit Patient is hemodynamically stable Patient does not have a history of osteopenia Inclusion criteria for reconstructive patients Child is between ages 4 to 18 Patients have sustained a 30% or greater tbsa in the last 10 years Patients must be of Black, White or Hispanic descent Live in Northeastern USA Inclusion criteria for healthy children Child is between ages 4 to 18 Patients must be of Black, White or Hispanic descent Live in Northeastern USA Child is capable of cooperating during measurement