Multiple myeloma (MM) accounts for 10% of the malignant haematological diseases and approximately 1% of all cancer-related deaths in Western countries. MM is characterised by the accumulation of malignant plasma cells in the bone marrow leading to impaired haematopoiesis and the highest incidence of bone involvement among the malignant diseases. MM bone disease is the result of increased destruction of bone that cannot be compensated for by new bone formation. Approximately 80% of patients with MM develop skeletal complications including bone pain, hypercalcemia, osteoporosis, osteolytic lesions and pathologic fractures. Vertebral fractures may be associated with spinal cord compression and neurological complications requiring surgery and/or radiotherapy. Osteolytic bone destruction is the most debilitating manifestation of MM, has a severe impact on patients' quality of life and is responsible for increased morbidity and mortality. Furthermore, bone resorption activity has been shown to be an independent risk factor for overall survival in patients with symptomatic MM. Moreover, myeloma-associated lytic bone lesions do not repair, even in patients who are disease free for years.