<prompt> The most common manifestation of osteoporosis is:Compression fracture of the spineAsymptomatic, detected incidentally by low serum CalciumBowing of legsLoss of weight  <response>: Answer is A Compression fracture of the spine : It most commonly presents as backache of varying degrees of severity. This backache is due to spontaneous fracture or collapse of veebra. Osteoporosis is defined as a reduction of bone mass or density, sufficient to increase the risk offracture. Osteoporosis is usually asymptomatic until fracture occurs but serum Calcium is normal Q. Serum parathyroid hormone, 25-OH D2, Calcium, Phosphorus and Alkaline phosphatase are usually normal. 