When bones break easily, the condition is most commonly called osteoporosis in adults or osteogenesis imperfecta (also known as brittle bone disease) in people born with it. These are two very different conditions with different causes, but both lead to fragile bones that fracture more easily than they should. A third condition, osteomalacia, causes bones to soften rather than become porous, and it can also increase fracture risk.
Osteogenesis Imperfecta: Brittle Bone Disease
Osteogenesis imperfecta (OI) is a genetic condition present from birth. It happens when the body either makes too little of a protein called type I collagen or makes it incorrectly. Collagen is the material that gives bones their strength and flexibility, so without enough of it, bones become weak and break with little or no force. Some children with OI fracture dozens of times before they reach adulthood. Others have a milder form and may not be diagnosed until later in life.
OI affects more than just bones. People with it often have a blue or grayish tint to the whites of their eyes, a feature that can be visible even in infancy. About half develop hearing loss by adulthood. Many also have a dental condition that causes teeth to appear brownish or opalescent gray, with enamel that chips easily. Short stature, curvature of the spine, and loose joints are also common.
Type I is the mildest form and the most common. People with Type I OI may break bones more often than average, especially during childhood, but they typically have near-normal stature and fewer skeletal deformities. More severe types can cause bones to bow or deform, significant short stature, and respiratory problems from a small or misshapen rib cage.
Osteoporosis: The Most Common Cause in Adults
Osteoporosis is far more common than OI and develops over time rather than being present at birth. The word literally means “porous bone.” In healthy bone, your body constantly breaks down old bone tissue and replaces it with new bone in a balanced cycle. Osteoporosis develops when the cells that break down bone outpace the cells that build it back up, leaving bones thinner, more porous, and significantly weaker.
Estrogen plays a major role in keeping that cycle balanced, which is why osteoporosis is especially common after menopause. The drop in estrogen increases the number of bone-breaking cells while simultaneously decreasing the number of bone-building cells. This creates a sustained imbalance that accelerates bone loss over years. Men can develop osteoporosis too, though it tends to happen later and less frequently.
Osteoporosis is often called a “silent” condition because you can lose a significant amount of bone density without feeling anything. The first sign is frequently a fracture, often in the hip, spine, or wrist, from a fall that wouldn’t have caused a break in someone with healthy bones. Spinal compression fractures can happen gradually, leading to a loss of height or a hunched posture over time.
How Bone Density Is Measured
A bone density scan (called a DXA scan) measures how much mineral is packed into your bones and produces a number called a T-score. A T-score of negative 1 or higher is considered healthy. Between negative 1 and negative 2.5 indicates osteopenia, a less severe stage of bone loss that signals increased risk. A T-score of negative 2.5 or lower is the threshold for an osteoporosis diagnosis.
Current screening guidelines recommend bone density testing for all women 65 and older. Postmenopausal women younger than 65 should be screened if they have risk factors like low body weight, smoking, a family history of hip fractures, or long-term use of certain medications. There isn’t enough evidence yet to make a firm screening recommendation for men, though doctors may suggest testing for those with clear risk factors.
Osteomalacia: Soft Bones, Not Porous Ones
Osteomalacia is sometimes confused with osteoporosis, but the two are fundamentally different. In osteoporosis, the internal structure of bone deteriorates and becomes porous. In osteomalacia, the bone’s architecture stays intact, but the minerals that harden it (primarily calcium and phosphorus) are depleted. The result is bones that are soft rather than brittle. Think of it as the difference between a sponge with too many holes (osteoporosis) and a sponge that never fully dried (osteomalacia).
The most common cause of osteomalacia is severe vitamin D deficiency, since vitamin D is essential for your body to absorb calcium from food. In children, this same process is called rickets. Blood tests in people with osteomalacia typically show low calcium, low phosphorus, and elevated levels of an enzyme called alkaline phosphatase, whereas these values are usually normal in osteoporosis.
Medications That Weaken Bones
Some widely prescribed medications can cause bones to thin over time, a problem many doctors and patients underestimate. Glucocorticoids (steroids used for conditions like asthma, rheumatoid arthritis, and inflammatory bowel disease) are the most well-known culprits. Even low doses are associated with increased fracture risk, and 30 to 50 percent of people on long-term glucocorticoid therapy develop fractures. The good news is that fracture risk generally returns to baseline within about two years of stopping these medications.
Glucocorticoids are far from the only offenders. Acid-reducing medications used for heartburn, certain antidepressants, anti-seizure drugs, some diabetes medications, hormone-blocking cancer treatments, blood thinners, and some chemotherapy agents all have documented harmful effects on bone density. If you take any of these long term, it’s worth asking whether bone monitoring makes sense for you.
How Bone Fragility Is Treated
For osteoporosis, the most commonly prescribed medications work by slowing down the cells that break down bone. These drugs can meaningfully reduce fracture risk: some reduce spinal fractures by up to 70 percent and hip fractures by about 35 percent. They’re typically taken as a weekly or monthly pill, or in some cases as a yearly infusion. Other medications take the opposite approach and stimulate new bone growth rather than just slowing bone loss.
For osteogenesis imperfecta, treatment focuses on strengthening existing bone, preventing fractures, and managing pain. Children with moderate to severe OI may undergo a procedure where metal rods are placed inside long bones to provide internal support. Physical therapy plays a central role in building muscle strength, which helps protect bones. The same class of medications used for osteoporosis is also used in children with OI to increase bone density.
For osteomalacia, treatment is more straightforward. Because the underlying problem is a mineral deficiency, correcting vitamin D and calcium levels through supplements usually allows bones to re-mineralize and regain their normal hardness over several months.
Risk Factors You Can and Cannot Change
Some risk factors for bone fragility are outside your control: being female, having a small frame, being white or Asian, having a family history of fractures, and reaching older age all increase risk. Early menopause or surgical removal of the ovaries accelerates bone loss because of the sudden drop in estrogen.
Other factors are modifiable. Smoking accelerates bone loss. Heavy alcohol use interferes with the bone-building cycle. A diet low in calcium and vitamin D deprives bones of the raw materials they need. Physical inactivity is a major contributor because bone responds to mechanical stress. Weight-bearing exercise like walking, jogging, and resistance training stimulates bone-building cells and helps maintain density throughout life. Even people already diagnosed with osteoporosis benefit from regular exercise, both for bone health and for the balance and muscle strength that help prevent falls in the first place.