The bones most vulnerable to osteoporosis are the spine (thoracic and lumbar vertebrae), the hip (specifically the femoral neck), and the wrist (the distal radius and ulna). These three sites account for the vast majority of osteoporotic fractures, and they share a common trait: a high proportion of spongy, porous bone tissue that loses density faster than the dense outer bone found in places like the shin or skull. Beyond these primary sites, the upper arm (humerus), pelvis, and ribs also fracture at elevated rates in people with osteoporosis.
Why Certain Bones Break First
Your skeleton contains two types of bone tissue. The hard, smooth outer layer is called cortical bone. The inner lattice, which looks like a honeycomb or sponge under a microscope, is called trabecular bone. Both lose density with age, but trabecular bone is far more vulnerable to osteoporosis because of how bone remodeling works.
Your body constantly breaks down old bone and replaces it with new bone, a process that happens on bone surfaces. Trabecular bone has a massive surface area relative to its mass. In people under 65, trabecular bone makes up only about 20% of total skeletal mass yet is responsible for most of the body’s bone turnover. That means when the balance between bone breakdown and bone rebuilding tips in the wrong direction, trabecular bone deteriorates first and fastest. The spine, hip, and wrist all contain large amounts of trabecular bone, which is why early osteoporosis shows up at these sites before it affects denser bones elsewhere.
The Spine: The Most Common Fracture Site
Vertebral fractures are the single most common type of osteoporotic fracture. In a large U.S. study tracking fracture rates from 2007 to 2017, spinal fractures occurred at a rate of 3.44 per 1,000 person-years, roughly double the rate of hip fractures. The vertebral bodies in the mid-back (thoracic) and lower back (lumbar) regions are especially at risk.
The reason is partly structural. Vertebral bodies are filled with trabecular bone and bear the full compressive load of your upper body weight, plus any force from bending, twisting, or lifting. When bone density drops, the vertebra can no longer withstand normal axial loading. It collapses, usually at the front, producing a characteristic wedge-shaped deformity called a compression fracture. The thoracolumbar junction, where the rigid thoracic spine meets the more flexible lumbar spine, is particularly prone because the transition between these segments concentrates mechanical stress.
One compression fracture can trigger a cascade. The resulting forward curvature (kyphosis) shifts the body’s center of gravity and places additional stress on neighboring vertebrae, raising the risk of further fractures. Each vertebral fracture reduces height by about half a centimeter on average. That height loss isn’t just cosmetic: it compresses the chest cavity. Research in postmenopausal women with osteoporosis found that for each unit increase in spinal deformity, forced inspiratory lung capacity dropped by roughly 1.6%. Over multiple fractures, this can meaningfully limit breathing.
The Hip: The Most Serious Fracture
Hip fractures, specifically fractures of the femoral neck, are the most dangerous consequence of osteoporosis. The femoral neck is the short, angled bridge of bone connecting the ball of the hip joint to the shaft of the thighbone. It bears enormous forces during walking, standing, and especially falling, and it contains a significant proportion of trabecular bone that thins with age.
Femoral neck fractures account for roughly 49 to 57% of all hip fractures. The primary driver is reduced bone mineral density, but the geometry of the femoral neck also matters. As the cortical shell of the femoral neck thins and its internal trabecular scaffolding weakens, the bone’s ability to absorb the impact of a sideways fall drops dramatically. A fall that a healthy 30-year-old would walk away from can shatter the femoral neck in someone with osteoporosis.
The consequences are severe. Cumulative one-year mortality after an osteoporotic hip fracture is approximately 30% in women and 43% in men. Only 30 to 40% of patients recover their previous level of physical function. Three-year mortality reaches 53% in women and nearly 66% in men. These numbers make hip fracture prevention one of the central goals of osteoporosis treatment.
The Wrist: Often the First Warning Sign
Wrist fractures, specifically breaks at the lower end of the radius near the wrist joint, tend to happen earlier in the progression of osteoporosis than hip or spinal fractures. They occur when someone trips and instinctively reaches out to catch themselves, driving the full force of the fall through an outstretched hand. The distal radius, rich in trabecular bone, absorbs that impact and snaps.
In fracture incidence data, the radius and ulna rank as the second most common osteoporotic fracture site after the spine. Because wrist fractures tend to happen in people who are still active and mobile enough to fall forward and brace themselves (rather than collapsing sideways as frailer individuals do), they often occur in people in their 50s and 60s. A wrist fracture at this age can be an early signal that bone density has already dropped significantly.
Other Vulnerable Sites
The “classic four” fracture sites in osteoporosis are the spine, hip, wrist, and upper arm, but other bones are affected too. The humerus (upper arm bone) fractures when weakened trabecular bone near the shoulder joint gives way, typically during a fall. The pelvis is another site with high trabecular content that fractures under relatively minor stress in people with low bone density. Rib fractures can occur from something as ordinary as a strong cough or a tight hug.
A multidisciplinary expert panel evaluating fracture attribution found that beyond the vertebrae, femoral neck, and distal radius, the pelvis and humeral shaft were among the fracture sites most clearly linked to underlying osteoporosis. These secondary sites don’t get as much attention, but they cause real pain and disability, and they signal the same underlying problem: too little bone where the body needs it most.
How Bone Density Is Measured
Osteoporosis is diagnosed using a DEXA scan, which measures bone mineral density and compares it to the peak bone density of a healthy young adult. The result is expressed as a T-score. A T-score of negative 1.0 or above is normal. Between negative 1.0 and negative 2.5 indicates osteopenia, a milder degree of bone loss. A T-score at or below negative 2.5 is the threshold for an osteoporosis diagnosis. These criteria, established by the WHO in 1994, remain the standard today.
DEXA scans are typically performed at the spine and hip because these sites contain the trabecular bone that reflects early changes in density most reliably. If you’ve already had a fracture from a minor fall or impact, that fracture itself may be the strongest indicator that your bones have weakened, regardless of what a scan shows.