About 60 subjects (7 to 21 years old) will be enrolled on this study, 30 with chronic pain and 30 without chronic pain. The investigators will assess baseline characteristics including vitamin D levels, bone turnover rates (measured by C telopeptide blood levels [CTx]), markers of inflammation and oxidative stress levels in blood, baseline hemoglobin and other laboratory parameters, presence of abnormal bones on chest x-ray, pulmonary function, opioid analgesic use, overall muscle strength, quality of life and depression.