Which condition is primarily marked by a decrease in bone density?

Osteoporosis is primarily marked by a significant decrease in bone density, which leads to an increased risk of fractures and breaks. This condition occurs when the creation of new bone doesn’t keep up with the removal of old bone, resulting in bones that become weak and brittle. In osteoporosis, the bone density is significantly lower than normal, often diagnosed through bone density scans.

Osteopenia, while related, is a less severe form of bone loss compared to osteoporosis and is also characterized by decreased bone density, but it is not as advanced or concerning as osteoporosis itself. Arthritis, on the other hand, refers to inflammation of the joints and does not primarily concern bone density. Rickets is a condition found in growing children that results from a deficiency in vitamin D, calcium, or phosphate leading to softening and weakening of bones but does not primarily denote a generalized decrease in bone density as seen in osteoporosis.