Osteosclerosis refers to an abnormal hardening of bone tissue, which is due to decreased bone resorption, and increased bone formation. This can be caused by several different factors, including osteomyelitis, hyperparathyroidism, multiple myeloma, and bisphosphonate intoxication. Affected people may present with bone pain, and decreased mobility. pathologic fractures and deformities. Treatment involves addressing the cause, administering Vitamin D, pain management, and treating fractures as they arise.