What is osteonecrosis (avascular necrosis) and what are the causes of the associated pain?

Osteonecrosis, also known as avascular necrosis or ischemic necrosis, is a medical condition resulting from the interruption or reduction of blood flow to a portion of bone. Living bone cells require a continuous blood supply to remain healthy. When this supply is cut off, the bone tissue dies, leading to gradual weakening and collapse of the bone, particularly in weight-bearing joints [3].

Osteonecrosis can affect any bone in the body, but it frequently impacts the ends of long bones, such as the top of the femur (the ball of the hip joint) and the top of the humerus (the ball of the shoulder joint), as well as the knees and ankles [3]. Deterioration of the bone in the affected joint leads to loss of function and may progress to arthritis.

Causes of Pain in Osteonecrosis

In the initial stages, there may be no symptoms of osteonecrosis. As the disease progresses, pain begins to appear gradually and worsens over time [2]. Pain is typically the primary symptom and is often felt in weight-bearing joints, such as the hip, where it is usually sensed in the groin or buttock area [3].

• Pain during movement and at rest: Initially, most people feel pain when putting weight on the affected joint. As the condition worsens, the joint may become painful even at rest [3].
• Stiffness and loss of range of motion: Over time, the joint may become stiff and lose its normal range of motion, leading to difficulty in bending or moving the affected joint [2].
• Sudden collapse: If the end of the bone collapses, pain may increase suddenly and severely [3].

Major Risk Factors

The exact cause of osteonecrosis is not fully understood in all cases, but several factors increase the risk of developing it [2]:

• Injuries: Fractures, bone dislocations, or joint injuries can damage surrounding blood vessels, reducing blood flow to the bone and causing avascular necrosis [3].
• Medications: Long-term use of high-dose corticosteroids (cortisone) increases the risk of osteonecrosis, although the exact mechanism is unclear [3].
• Alcohol and tobacco consumption: Excessive use of alcohol and tobacco is considered a risk factor. Excessive alcohol consumption may lead to the accumulation of fatty substances in blood vessels and increased cortisol levels, which reduces blood flow to the bone [3].
• Medical conditions: Certain diseases such as sickle cell anemia, leukemia, Gaucher's disease, systemic lupus erythematosus, and pancreatitis may increase the risk of developing the condition [3].
• Medical interventions: Chemotherapy, organ transplantation (due to the use of corticosteroids to prevent rejection), and radiation therapy can increase the risks [3].

Early Diagnosis

Early diagnosis of osteonecrosis is crucial to prevent further bone and joint damage. Doctors rely on imaging methods to diagnose the condition, such as X-rays and magnetic resonance imaging (MRI) [3]. In early stages, X-rays may not show changes, whereas MRI is more sensitive in detecting the disease in its early phases.

Treatment Options

Treatment options aim to relieve pain, improve joint function, and prevent further bone damage. Initial treatments may include pain medication, physical therapy, modification of activities to reduce stress on the affected joint, and the use of assistive devices such as crutches [1].

In many cases, osteonecrosis may require surgical intervention to protect the bones and joints and improve their use [3]. A common surgical option is hip replacement surgery, where damaged parts of the joint are removed and replaced with artificial parts. This surgery can relieve pain, improve joint function, and increase mobility [1].

For more information about osteonecrosis and its treatment methods, you can visit Osteonecrosis: Causes, Diagnosis, and Treatment (Arabic).

Medical references

• Osteonecrosis
• Osteonecrosis
• Hip Replacement Surgery