Biochemical tests are used to diagnose bone diseases. Serum tests measure calcium, phosphate, alkaline phosphatase, parathyroid hormone, and vitamin D levels. Urine tests measure calcium, phosphate, and bone turnover markers. Common bone diseases include arthritis, osteoporosis, rickets/osteomalacia, and Paget's disease. Arthritis causes joint symptoms. Osteoporosis weakens bones and increases fracture risk. Rickets/osteomalacia cause soft bones from vitamin D deficiency. Paget's disease involves abnormal bone remodeling.