Diagnosing Osteonecrosis

Osteonecrosis, also known as avascular necrosis, is the degeneration of bone tissue caused by too little blood supplied to the bone. At NYU Langone Orthopedic Hospital, our surgeons specialize in diagnosing this condition, and can recognize the early signs of the disease before it causes permanent damage.

Bones are made of living tissue, in which new cells continually replace old ones. This cycle keeps bones strong and enables them to rebuild after an injury. Without the nourishment of oxygen-rich blood, bone cells begin to die, and small lesions form within the bone. These lesions get larger as the disease progresses. Without treatment, osteonecrosis may continue to progress until parts of the bone eventually collapse.

The disease most often affects joints involving the femur—the thighbone, which connects the hip to the knee—but osteonecrosis can occur in any bone. If the femur loses its blood supply at the hip, for example, lesions may cause the head of the bone, called the femoral head, to lose its rounded contours, compromising the smooth gliding surface that allows the hip joint to move easily. Extensive damage to the surface of the joint may lead to an erosion of cartilage and arthritis.

Symptoms of this condition include joint pain that is usually mild at first and may only be noticeable if you put weight on the affected joint. If the disease progresses and causes more severe damage, you may feel aching pain all the time and have difficulty moving the joint.

Risk Factors

Rarely, osteonecrosis can develop without an identifiable cause, but certain risk factors increase the chance that osteonecrosis may occur. These include a bone fracture or dislocation, which can injure blood vessels and cut off a bone’s blood supply. Surgery to repair a fracture or to replace a joint with artificial parts may also disrupt blood supply.

Corticosteroid medication, which is often prescribed to help people with medical conditions such as inflammatory bowel disease or allergic reactions, may interfere with blood supply to bones. The use of radiation therapy and chemotherapy drugs is also a risk factor. The reasons these therapies are linked to osteonecrosis are unclear, but some research suggests that just one dose increases the risk.

Research also suggests that certain illnesses are associated with osteonecrosis. These include HIV infection, sickle cell disease, Gaucher’s disease, Caisson’s disease, osteoporosis, kidney disease, liver disease, and gout. All of these disorders may lead to a disruption in blood supply to a bone through different mechanisms.

Alcohol use also increases risk. Excessive drinking, even for a short time, can lead to fatty deposits building up in blood vessels, decreasing blood flow to the bones. Avoiding alcohol is the best way to reduce this risk.

Early diagnosis is vital to stopping the progression of osteonecrosis and preserving a joint before arthritis develops. If you have one or more risk factors and experience joint pain, our orthopedic specialists recommend evaluation to determine if osteonecrosis is the cause.

At NYU Langone, doctors use an MRI scan or X-ray to diagnose osteonecrosis and determine the extent of damage to the bones.

Medical History and Physical Examination

A doctor examines the area where you feel pain and asks you about your medical and family history, symptoms, and lifestyle. If you feel discomfort in a joint such as a knee or hip, your doctor may also ask you to stand and walk so that he or she can assess whether symptoms affect your gait or cause a limp. Your doctor may also ask you to bend or move your leg in different positions to evaluate your range of motion.

X-Rays

X-rays use electromagnetic waves to create pictures of bones inside the body. A doctor can confirm the presence of osteonecrosis lesions on an X-ray if the disease has progressed. X-rays also are used to monitor the progression of the disease throughout treatment.

MRI Scans  

An MRI scan can reveal small lesions that form within a bone as a result of osteonecrosis. The condition is often diagnosed using an MRI scan even when no evidence is visible on an X-ray. For this reason, MRI scans are preferable for early detection.

An MRI scan uses a magnetic field and radio waves to create computerized, three-dimensional images of bones and joints. Doctors use these images to examine bones from a variety of angles, allowing them to detect lesions or other damage.