Avascular Necrosis
Avascular necrosis, also called osteonecrosis, is a painful condition that develops when part of a bone loses its blood supply. Bone tissue depends on a steady flow of oxygen and nutrients carried through blood vessels. When that blood flow becomes reduced or completely blocked, the bone tissue begins to weaken and die over time. As the condition progresses, the affected bone can collapse, leading to arthritis, chronic pain, stiffness, and loss of joint function.
Avascular necrosis can affect several areas of the body, but it most commonly develops in the hip. The shoulder, knee, ankle, and wrist may also be affected. In some cases, more than one joint develops avascular necrosis at the same time. Many people are surprised to learn that the condition can progress quietly in the early stages before significant symptoms appear.
The hip is particularly vulnerable because the blood supply to the femoral head, which is the ball portion of the hip joint, can be disrupted relatively easily. Once the bone begins to collapse, the smooth surface of the joint becomes uneven. This causes friction, inflammation, pain, and eventually arthritis.
Avascular necrosis is considered a serious orthopedic condition because it tends to worsen without treatment. Early diagnosis is important because treatment is generally more successful before the bone collapses.
Avascular necrosis develops when blood flow to a bone becomes interrupted or severely reduced. There are several possible reasons this may happen, and sometimes the exact cause is never fully identified.
- Trauma is one of the most common causes. A fracture or dislocation can damage nearby blood vessels and reduce circulation to the bone. Hip fractures and hip dislocations are particularly associated with avascular necrosis because they may disrupt the delicate blood supply to the femoral head.
- Long-term corticosteroid use is another major risk factor. Steroid medications are commonly prescribed to treat inflammation, autoimmune diseases, asthma, and other medical conditions. Although these medications can be extremely effective, prolonged or high-dose steroid use may interfere with blood circulation within the bone. The exact mechanism is not completely understood, but steroids appear to increase fat deposits within blood vessels, making it harder for blood to flow properly.
- Excessive alcohol consumption is also strongly linked to avascular necrosis. Heavy alcohol use may cause fatty substances to build up in blood vessels, reducing circulation to bone tissue over time. In addition, alcohol can directly affect bone health and healing.
- Certain medical conditions may increase the risk as well. These include sickle cell disease, lupus, blood clotting disorders, kidney disease, organ transplantation, and some autoimmune conditions. Radiation therapy and chemotherapy may also damage blood vessels and weaken bone tissue.
In some patients, avascular necrosis develops without any clear injury or medical explanation. This is called idiopathic avascular necrosis. Even without an obvious cause, the underlying problem remains the same: the bone is not receiving enough blood flow to remain healthy.
The symptoms of avascular necrosis usually develop gradually. Early in the disease process, some people have little or no pain. As the condition worsens and the bone begins to weaken, symptoms become more noticeable.
Pain is the most common symptom. The discomfort often begins as a mild ache that gradually increases over time. In hip avascular necrosis, pain is commonly felt in the groin, buttock, or upper thigh. Some patients also experience pain that radiates toward the knee. Shoulder avascular necrosis may cause aching deep within the shoulder joint, especially during overhead movements.
At first, pain may only occur during weight-bearing activities such as walking, climbing stairs, exercising, or standing for prolonged periods. As the condition progresses, pain can become constant and may even occur at rest or during sleep.
Stiffness and reduced range of motion are also common. Patients may notice difficulty bending, rotating, or moving the affected joint normally. Limping may develop when the hip is involved because the joint no longer moves smoothly or comfortably.
Bone collapse occurs when the weakened bone structure can no longer support normal body weight and joint movement. As bone collapse occurs, symptoms typically become more severe. The joint surface becomes irregular, leading to cartilage damage and arthritis. At this stage, patients often experience significant pain, grinding sensations, weakness, and major limitations in mobility.
The progression of symptoms can vary widely from person to person. Some individuals deteriorate rapidly over several months, while others experience slower progression over years.
Diagnosing avascular necrosis begins with a thorough medical history and physical examination. An OrthoIllinois orthopedist will ask about symptoms, injuries, medication use, alcohol intake, and underlying medical conditions that may increase risk.
During the physical examination, the affected joint is evaluated for pain, stiffness, weakness, and limited movement. Certain movements may reproduce pain or reveal restricted motion within the joint.
Imaging studies are essential for confirming the diagnosis. X-rays are often the first test performed. In the early stages of avascular necrosis, X-rays may appear normal because bone damage has not yet become visible. As the disease advances, X-rays may show areas of bone collapse, flattening of the joint surface, or signs of arthritis.
Magnetic resonance imaging, commonly called MRI, is considered the most sensitive test for detecting avascular necrosis. MRI scans can identify early bone damage before it becomes visible on X-rays. This is important because early diagnosis provides a better opportunity to slow progression and preserve the joint.
CT scans may also be used to evaluate the extent of bone collapse and joint damage in more advanced cases. Bone scans are less commonly used today but may sometimes help identify areas of reduced blood flow.
Because avascular necrosis can mimic other orthopedic conditions, accurate diagnosis is critical. Conditions such as arthritis, labral tears, tendon injuries, bursitis, and stress fractures can produce similar symptoms. Proper evaluation helps determine the exact cause of pain and guides treatment decisions.
Early recognition of avascular necrosis can make a major difference in preserving joint function and delaying or preventing severe joint damage. When you or a loved one suffers with joint pain, contact OrthoIllinois to schedule a consultation to evaluate your pain and discuss your condition. OrthoIllinois is a premier orthopedic care provider in Northern Illinois.
