When you read about osteoporosis, you will come across medical terms that can feel confusing or intimidating. This glossary is here to help. Every term is explained in plain English, with links to our detailed articles where you can learn more.
This glossary is for general reference only and does not replace professional medical advice. If you have questions about a specific term or how it relates to your health, please speak with your doctor.
A
Abaloparatide — A bone-building medication (anabolic agent) that stimulates new bone formation. It is given as a daily self-injection under the skin. Abaloparatide works similarly to teriparatide but is a newer option. Treatment is limited to a maximum of two years. → Teriparatide & Abaloparatide
Alendronate — One of the most widely prescribed bisphosphonate medications for osteoporosis. It has been used for over 25 years and is typically taken as a weekly tablet on an empty stomach. → Bisphosphonates
Anabolic agent — A type of osteoporosis medication that builds new bone by stimulating osteoblasts (the bone-building cells). Examples include teriparatide, abaloparatide, and romosozumab. These are generally reserved for people at high risk of fracture. → Treatment Overview
Antiresorptive — A category of osteoporosis medications that slow down bone loss by reducing the activity of osteoclasts (the cells that break down bone). Bisphosphonates, denosumab, and estrogen therapy are all antiresorptive agents. → Treatment Overview
Atypical femoral fracture (AFF) — A rare type of fracture that occurs in the thigh bone (femur), sometimes associated with long-term use of bisphosphonates or denosumab. Unlike typical fractures, AFFs can start as a stress reaction and may cause thigh or groin pain before the bone breaks completely. They are uncommon, and the benefits of treatment usually outweigh the risk. → Rare Side Effects
B
Bisphosphonate — The most commonly used class of osteoporosis medications. Bisphosphonates work by attaching to the bone surface and slowing down the cells (osteoclasts) that break down bone. Available as daily, weekly, or monthly tablets, or as a once-yearly intravenous infusion. Examples include alendronate, risedronate, ibandronate, and zoledronic acid. → Bisphosphonates
Bone mineral density (BMD) — A measurement of how much mineral (primarily calcium) is packed into a section of bone. Higher density generally means stronger bones. BMD is measured by a DXA scan and reported as a T-score. → DEXA Scans Explained
Bone remodeling — The lifelong process in which old bone is broken down (resorption) and replaced with new bone (formation). In healthy adults, this process is balanced. In osteoporosis, resorption outpaces formation, leading to weaker bones. → Your Bones Are Alive
Bone turnover markers — Blood or urine tests that measure how quickly bone is being broken down and rebuilt. Formation markers (like P1NP) show how much new bone is being made, while resorption markers (like CTX or NTX) show how much bone is being lost. Doctors use these to monitor treatment effectiveness. → Bone Turnover Markers
C
Calcium — The most abundant mineral in your bones, essential for bone strength. Adults generally need 1,000-1,200 mg per day from food and supplements combined. Good dietary sources include dairy products, leafy green vegetables, fortified foods, and canned fish with bones. → Eating for Strong Bones
Compression fracture — A type of fracture in which a vertebra (a bone in the spine) collapses or becomes wedge-shaped. Compression fractures are the most common type of osteoporotic fracture. Many occur without significant pain and may only be discovered through height loss or changes in posture. → The Silent Disease
Cortical bone — The dense, hard outer layer of bone that forms the outer shell. Cortical bone makes up about 80% of total bone mass and provides structural strength. The inner part of bone is trabecular (spongy) bone. → Your Bones Are Alive
D
Denosumab — A medication given as a subcutaneous injection every six months. It works by blocking RANKL, a protein that signals osteoclasts to break down bone. Denosumab is effective at reducing fractures, but it is critical never to miss or delay a dose, as stopping can cause rapid bone loss. → Denosumab
Drug holiday — A planned break from bisphosphonate treatment, typically considered after 3-5 years of oral bisphosphonates or 3 years of intravenous zoledronic acid in patients whose fracture risk has decreased. During a drug holiday, bisphosphonates continue to work from the bone reservoir built up during treatment. Drug holidays do not apply to denosumab or anabolic agents. → Staying on Track
DXA (Dual-energy X-ray Absorptiometry) — The gold standard test for measuring bone mineral density. A DXA scan is quick (10-15 minutes), painless, and uses very low radiation -- less than a standard chest X-ray. Results are reported as a T-score. Sometimes written as DEXA. → DEXA Scans Explained
E
Estrogen — A hormone produced primarily by the ovaries that plays a crucial role in maintaining bone density. Estrogen acts like a shield, keeping osteoclasts (bone-breaking cells) in check. After menopause, estrogen levels drop sharply, leading to accelerated bone loss -- this is why osteoporosis is more common in postmenopausal women. → Estrogen and Your Bones
F
Fragility fracture — A fracture that results from a fall from standing height or less, or from minimal trauma that would not normally break healthy bone. Examples include breaking a wrist by catching yourself during a stumble, or fracturing a vertebra while lifting a bag of groceries. A fragility fracture is a strong indicator of osteoporosis. → The Silent Disease
FRAX — A fracture risk assessment tool developed by the World Health Organization (WHO). FRAX uses clinical risk factors (with or without bone density data) to calculate your 10-year probability of a major osteoporotic fracture or hip fracture. It is available free online and is used by doctors worldwide. → FRAX
H
Hip fracture — A fracture of the upper part of the thigh bone (femur), near where it meets the pelvis. Hip fractures are the most serious consequence of osteoporosis, almost always requiring surgery and hospitalization. They can significantly affect independence, mobility, and quality of life. → The Silent Disease
Hormone replacement therapy (HRT) — Treatment that replaces estrogen (and sometimes progesterone) after menopause. HRT can help maintain bone density and reduce fracture risk, but it also carries other health considerations. It is typically prescribed for menopausal symptoms rather than solely for bone health. → Estrogen and Your Bones
I
Ibandronate — A bisphosphonate medication available as a monthly oral tablet or a quarterly intravenous injection. Like other bisphosphonates, it works by slowing bone breakdown. → Bisphosphonates
IOF (International Osteoporosis Foundation) — A global non-profit organization dedicated to fighting osteoporosis and related musculoskeletal diseases. IOF provides patient resources, supports research, and advocates for better bone health policies worldwide. Website: https://www.osteoporosis.foundation/
K
Kyphoplasty — A minimally invasive surgical procedure used to treat painful vertebral compression fractures. A small balloon is inserted into the collapsed vertebra and inflated to restore height, then the space is filled with bone cement. → Fracture Treatment Options
Kyphosis — An increased forward rounding of the upper back, sometimes called a "dowager's hump." Kyphosis in older adults is often caused by multiple vertebral compression fractures. It can affect breathing, balance, and quality of life. → The Silent Disease
M
Menopause — The point in a woman's life when menstrual periods stop permanently, typically occurring between ages 45 and 55. The sharp decline in estrogen production during menopause is the primary trigger for accelerated bone loss in women. → Estrogen and Your Bones
Mineral — In the context of bone health, minerals are inorganic substances (primarily calcium and phosphorus) that give bone its hardness and strength. Bone mineral content is what DXA scans measure.
MK-7 (menaquinone-7) — A form of vitamin K2 found in fermented foods such as natto (fermented soybeans), certain cheeses, and sauerkraut. MK-7 helps activate osteocalcin, a protein that directs calcium into bone. It stays active in the body longer than other forms of vitamin K. → Vitamin K Foods
N
NOF (National Osteoporosis Foundation) — Now known as the Bone Health & Osteoporosis Foundation (BHOF), this is the leading US non-profit organization dedicated to preventing osteoporosis and broken bones. Website: https://www.bonehealthandosteoporosis.org/
NTX (N-terminal telopeptide) — A bone turnover marker measured in blood or urine that indicates how quickly bone is being broken down (a bone resorption marker). Doctors may use NTX levels to assess fracture risk and monitor treatment response. → Bone Turnover Markers
O
Osteoblast — A cell responsible for building new bone. Osteoblasts produce the collagen framework and then deposit calcium and other minerals to harden it. Think of osteoblasts as the "construction crew" of bone remodeling. → Your Bones Are Alive
Osteoclast — A cell responsible for breaking down old or damaged bone. Osteoclasts dissolve both the mineral and protein components of bone, creating small cavities that osteoblasts later fill with new bone. Think of osteoclasts as the "demolition crew." In osteoporosis, osteoclasts work faster than osteoblasts can keep up with. → Your Bones Are Alive
Osteocyte — The most abundant cell in bone, formed when an osteoblast becomes embedded in the bone it has built. Osteocytes act as sensors, detecting mechanical stress and signaling when bone needs to be repaired or reinforced. They orchestrate the communication between osteoblasts and osteoclasts. → Your Bones Are Alive
Osteonecrosis of the jaw (ONJ) — A rare condition in which a section of jawbone fails to heal after dental work, remaining exposed for more than eight weeks. ONJ has been associated with antiresorptive medications (bisphosphonates and denosumab), though it is very uncommon. Good oral hygiene and regular dental checkups significantly reduce the risk. → Rare Side Effects
Osteopenia — A condition where bone mineral density is lower than normal but not low enough to be classified as osteoporosis. On a DXA scan, osteopenia corresponds to a T-score between -1.0 and -2.5. It can be thought of as a warning stage -- an opportunity to take action before osteoporosis develops. → DEXA Scans Explained
Osteoporosis — A condition in which bones become weak and brittle due to loss of bone mass and deterioration of bone structure, significantly increasing the risk of fractures. It is often called the "silent disease" because it typically causes no symptoms until a bone breaks. → The Silent Disease
P
P1NP (procollagen type 1 N-terminal propeptide) — A blood test that measures how much new bone is being formed (a bone formation marker). P1NP levels rise when osteoblasts are actively building bone. Doctors may use this test to monitor how well anabolic medications are working. → Bone Turnover Markers
Peak bone mass — The maximum amount of bone a person achieves, typically reached in the mid-to-late twenties. The higher your peak bone mass, the more "bone savings" you carry into later life. Peak bone mass is influenced by genetics, nutrition, exercise, and hormones during childhood and young adulthood.
PTH (parathyroid hormone) — A hormone produced by the parathyroid glands that regulates calcium levels in the blood. When calcium levels drop, PTH signals the body to release calcium from bones. Continuous high PTH causes bone loss, but intermittent doses (as in teriparatide therapy) paradoxically stimulate new bone formation. → Teriparatide & Abaloparatide
R
RANKL (receptor activator of nuclear factor kappa-B ligand) — A protein that signals osteoclasts to develop, activate, and survive. Denosumab works by blocking RANKL, thereby reducing bone breakdown. → Denosumab
Remodeling — See Bone remodeling above.
Risedronate — A bisphosphonate medication typically taken as a weekly or monthly tablet. Like alendronate, it slows bone loss by reducing osteoclast activity. It has been shown to reduce the risk of vertebral and hip fractures. → Bisphosphonates
Romosozumab — A medication that has a unique "dual action" -- it both builds new bone and slows bone breakdown at the same time. It is given as two subcutaneous injections once a month for 12 months, followed by an antiresorptive medication. Romosozumab works by blocking sclerostin, a protein that normally puts the brakes on bone formation. → Romosozumab
S
Sarcopenia — The age-related loss of muscle mass and strength. Sarcopenia often accompanies osteoporosis, and together they significantly increase the risk of falls and fractures. Exercise -- particularly resistance training -- helps prevent both conditions. → Exercise for Stronger Bones
Sclerostin — A protein produced by osteocytes that slows down bone formation. Romosozumab works by blocking sclerostin, effectively removing the brakes on bone building. → Romosozumab
Sequential therapy — A treatment strategy in which bone-building (anabolic) medications are given first, followed by bone-preserving (antiresorptive) medications. This approach is designed to first rebuild bone and then lock in the gains. The sequence matters -- starting with an anabolic agent followed by an antiresorptive is generally more effective than the reverse. → Treatment Overview
T
T-score — A number from a DXA scan that compares your bone density to that of a healthy 30-year-old adult. A T-score of 0 means your bone density is equal to the reference. A T-score of -1.0 to -2.5 indicates osteopenia (low bone mass). A T-score of -2.5 or lower indicates osteoporosis. → DEXA Scans Explained
Teriparatide — A synthetic form of parathyroid hormone (PTH) given as a daily self-injection. It stimulates osteoblasts to build new bone. Treatment is limited to a maximum of two years, after which an antiresorptive medication is needed to preserve the bone that was built. → Teriparatide & Abaloparatide
Trabecular bone — The spongy, honeycomb-like bone found inside the outer shell of cortical bone. Trabecular bone is especially abundant in the spine and the ends of long bones. It has a high surface area and remodels more rapidly than cortical bone, making it the first to be affected by osteoporosis. → Your Bones Are Alive
V
Vertebra (plural: vertebrae) — One of the individual bones that make up the spinal column. The human spine has 33 vertebrae. Vertebral compression fractures -- the most common type of osteoporotic fracture -- occur when a vertebra collapses or becomes wedge-shaped. → The Silent Disease
Vertebroplasty — A minimally invasive procedure in which bone cement is injected into a fractured vertebra to stabilize it and relieve pain. Unlike kyphoplasty, vertebroplasty does not use a balloon to restore vertebral height. → Fracture Treatment Options
Vitamin D — A vitamin essential for calcium absorption in the gut. Without adequate vitamin D, even a calcium-rich diet cannot effectively strengthen your bones. The body produces vitamin D when skin is exposed to sunlight, and it can also be obtained from fatty fish, egg yolks, fortified foods, and supplements. Many people worldwide are vitamin D deficient. → The Vitamin D Gap
Vitamin K2 — A vitamin that helps activate osteocalcin, a protein that directs calcium into bone rather than into blood vessels. Vitamin K2 is found in fermented foods and some animal products. The MK-7 form (see above) is particularly well-studied for bone health. Note: people taking warfarin (a blood thinner) should consult their doctor before increasing vitamin K intake. → Vitamin K Foods
Z
Z-score — A DXA scan result that compares your bone density to the average for people of your same age and sex. Z-scores are typically used for premenopausal women, men under 50, and children. A Z-score of -2.0 or lower is considered "below the expected range for age" and may prompt investigation into underlying causes.
Zoledronic acid — A bisphosphonate given as an intravenous (IV) infusion once a year. Because it is given directly into the bloodstream, it avoids the stomach-related side effects of oral bisphosphonates. Flu-like symptoms may occur for a day or two after the first infusion. → Bisphosphonates
If you come across a term in our articles that is not listed here, please let us know at [email protected] and we will add it.
The information on this page is provided for general educational purposes and does not replace professional medical advice. If you have questions about your bone health, please speak with your doctor.
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