The present invention relates to a dual energy X-ray apparatus and method for osteoporosis assessment and monitoring. The present invention takes a bone densitometry reading of a patient's wrist to assess osteoporosis and monitor bone loss condition by repeat measurements along with therapy. The bone densitometry system has an X-ray source, dual energy detectors, an arm-rest to place the patient's arm, a motion system to move the source-detector gantry along the patient's forearm, and a computer with a database to archive the wrist image, calculate the bone mineral density, maintain a history of patient information, and generate patient history reports.