Osteoporosis is a condition where your bones get weaker over time. Bone tissue, the strongest of the tissue cells, naturally looks a bit like a spider's web: it is densely compacted but has "holes" in the bone matrix. Over time, bone tissue dissolves. For those with osteoporosis, the bone tissue dissolves faster than new bone tissue is created, leading to brittle bones that are prone to breaking. Osteoporosis usually impacts older adults.
Rickets, unlike osteoporosis impacts children. It is the softening or weakening of the bones as a result of vitamin D deficiency. This is different from osteoporosis as it occurs over time with a lack of vitamin D, impacting development and growth. Without sufficient vitamin D, children who develop rickets can have delayed growth and pain in the spine, pelvis, and/or legs (bones that grow or accumulate more stress during the growing process).
Tetany differs from osteoporosis and rickets as it impacts nerves and not bone tissue. Tetany, or overstimulated nerves, can cause muscles to cramp or spasm, particularly in the extremities like the hands and feet, but can also impact the throat and larynx.
One similarity between tetany and both osteoporosis and tickets is that it can be caused by low calcium levels; for both osteoporosis and rickets prevention, doctors suggest taking calcium supplements in addition to vitamin D (which as previously mentioned helps prevent rickets in children).