Osteomalacia refers to a marked softening of your bones, most often caused by severe vitamin D deficiency. The softened bones of children and young adults with osteomalacia can lead to bowing during growth, especially in weight-bearing bones of the legs. Osteomalacia in older adults can lead to fractures. The most common symptoms of osteomalacia are pain in the bones and hips, bone fractures, and muscle weakness. Patients can also have difficulty walking.