Bone is a living, growing tissue that mainly consists of collagen and calcium. Bones provide a rigid framework, known as the skeleton, which protects soft organs and supports the body. Certain conditions can affect bone strength and flexibility and result in health complications.
Osteoporosis is a disease that results in a decrease in bone mass and mineral density. The quality and structure of the bone may also change. Osteoporosis can decrease bone strength and increase the risk of fracturing. The risk of osteoporosis increases with age and affects people of all ethnic groups. It most commonly affects non-Hispanic white females and Asian females.
Osteopenia refers to a decrease in bone mineral density below a normal level but not low enough for a doctor to classify it as osteoporosis. A T-score is a measure of bone density. A person with a T-score between -1 and -2.5 will receive a diagnosis of osteopenia, whereas a doctor would classify a T-score lower than -2.5 as osteoporosis. The prevalence of osteopenia is 4 times higher in females compared with males.
Paget’s disease is a condition that affects the bone remodeling process. This refers to the action by which the body breaks down old bone tissue and replaces it with new bone tissue. In people with this chronic condition, the process of rebuilding bones takes place at a faster rate, resulting in an unusual bone structure. This can either cause the bones to become softer or larger, making them more susceptible to complications such as bending or fractures.
Osteogenesis imperfecta (OI) is a disorder that causes the bones to fracture easily. Some people may also refer to OI as brittle bone disease. The condition results from a change or mutation in the genes that carry information for making a protein known as type I collagen. This protein is necessary for strong bones.
People with a family history of OI have a higher risk of having the disease as a person can inherit the gene mutation through one or both of their parents. There are different types of OI. The most common and mildest type is type I, while type II is the most severe.
Osteonecrosis, also known as avascular necrosis or aseptic necrosis, occurs when there is a disruption to a bone’s blood flow, leading to bone tissue death. This can cause the bone to break down and the joint to collapse. While osteonecrosis may occur in any bone in the body, it commonly affects the shoulders, hips, and knees. The condition occurs most often in people aged 20–50 years. These individuals also often have a history of trauma, corticosteroid use, or excessive alcohol intake.
Osteoarthritis is the most common form of arthritis. This condition affects the body’s joints by degrading cartilage, the tissue that covers the surface of joints. Osteoarthritis can also change the shape of bones. Osteoarthritis most frequently affects the hands, hips, and knees.
Osteomyelitis describes an infection or inflammation of the bone, with myelitis referring to inflammation of the fatty tissues within the bone. It typically occurs when a bacterial or fungal infection enters a bone from the bloodstream or surrounding tissue. It can happen at any age but is more common in young children.
Fibrous dysplasia occurs when abnormal fibrous tissue replaces healthy bone tissue. The unusual scar-like tissue makes the bone weaker. This can cause the bone to change shape and increase the risk of fractures. Fibrous dysplasia typically occurs due to a gene mutation that results in bone cells producing an abnormal type of fibrous bone. While it can develop in any bone, it occurs most often in the thigh bone, shin bone, ribs, skull, humerus, and pelvis.
Bone cancer and tumors
Bone cancer is an uncommon type of cancer that begins when cells in a bone start to grow out of control. Any of the cells in the bone can develop into cancer. Primary bone cancers are cancers that start in the bone. The most common types of primary bone cancers include osteosarcoma and Ewing sarcoma. Cancer cells can also spread to the bone from other areas of the body. Doctors refer to these as bone metastases. The most common site for bone metastases is the spine.
Osteomalacia, also known as bone softening, refers to a condition where the bone does not harden the way it should after forming. This metabolic bone disease occurs when there is incomplete mineralization of the bone. Mineralization refers to the process where minerals coat the inner layer of the bone, forming a hard outer shell. The incomplete formation of this shell leaves the collagen soft and vulnerable.
Rickets is a childhood bone condition similar to osteomalacia, but it occurs due to imperfect mineralization. It results in soft, weak bones, typically due to a vitamin D deficiency. Without sufficient vitamin D, the body cannot metabolise calcium and phosphorus, which are essential for proper bone development and growth. Vitamin D deficiency may result from inadequate nutrition, lack of sun exposure, or malabsorption.
An autoimmune condition occurs when the immune system attacks the body’s own cells, tissue, and organs. Bone diseases can develop secondary to some autoimmune diseases, increasing the risk of complications such as bone loss and fractures. These conditions include:
- Type I diabetes: People with this condition produce minimal or no insulin, meaning the body cannot absorb sugar from food easily. People with type I diabetes have a higher risk of developing osteoporosis.
- Systemic lupus erythematosus (SLE): This condition can result in widespread inflammation affecting many parts of the body. Some treatment options for SLE may put people at a higher risk of bone loss and fractures.
- Rheumatoid arthritis (RA): This condition causes the body’s immune system to attack the membranes around the joints and causes the cartilage to degrade. There is an increased risk of bone loss and fractures in people with RA.
- Celiac disease: This condition causes the body to develop an intolerance to gluten, a protein commonly present in food products such as wheat, rye, and barley. The immune system attacks and damages the lining of the small intestine. A person with untreated celiac disease may develop bone disease due to difficulty absorbing calcium, which is necessary for healthy bones.