osteonecrosis

Osteonecrosis is a disease caused by reduced blood flow to bones in the joints. In people with healthy bones, new bone is always replacing old bone. In osteonecrosis, the lack of blood causes the bone to break down faster than the body can make enough new bone. The bone starts to die and may break down.

You can have osteonecrosis in one or several bones. It is most common in the upper leg. Other common sites are your upper arm and your knees, shoulders and ankles. The disease can affect men and women of any age, but it usually strikes in your thirties, forties or fifties.

At first, you might not have any symptoms. As the disease gets worse, you will probably have joint pain that becomes more severe. You may not be able to bend or move the affected joint very well.

No one is sure what causes the disease. Risk factors include :

• Long-term steroid treatment
• Alcohol misuse
• Joint injuries
• Having certain diseases, including arthritis and cancer

Doctors use imaging tests and other tests to diagnose osteonecrosis. Treatments include medicines, using crutches, limiting activities that put weight on the affected joints, electrical stimulation and surgery.

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases

Your jaw is a set of bones that holds your teeth. It includes:

• The maxilla, which is the upper part of your jaw. It holds your top teeth in place and doesn't move. It also supports the muscles involved in chewing and facial expressions.
• The mandible, which is the lower part of your jaw. You move it when you talk or chew. It also holds your lower teeth in place.
• The temporomandibular joints (TMJs), which are two joints (one on each side) that connect your mandible to your skull.

Jaw problems can include:

• Fractures (broken bones).
• Dislocations, which are joint injuries that force the ends of your bones out of position.
• Temporomandibular disorders (TMDs), which are conditions that affect your TMJs.
• Osteonecrosis, which happens when the blood flow to part of your bone is disrupted. It can cause the bone to break down.
• Jaw tumors, which can be benign (not cancer) or cancer.
• Jaw defects, which are birth defects in which your jaw could be missing or deformed.

Diagnostic imaging tests are often used to diagnose jaw injuries and disorders. Your treatment will depend on which jaw problem you have.

Your bones help you move, give you shape and support your body. They are living tissues that rebuild constantly throughout your life. During childhood and your teens, your body adds new bone faster than it removes old bone. After about age 20, you can lose bone faster than you make bone. To have strong bones when you are young, and to prevent bone loss when you are older, you need to get enough calcium, vitamin D, and exercise. You should also avoid smoking and drinking too much alcohol.

Bone diseases can make bones easy to break. Different kinds of bone problems include:

• Low bone density and osteoporosis, which make your bones weak and more likely to break
• Osteogenesis imperfecta makes your bones brittle
• Paget's disease of bone makes them weak
• Bones can also develop cancer and infections
• Other bone diseases, which are caused by poor nutrition, genetics, or problems with the rate of bone growth or rebuilding

NIH: National Institute of Arthritis and Musculoskeletal and Skin Diseases