Overview
Avascular necrosis (osteonecrosis) occurs when bone loses blood supply, leading to bone death and joint collapse, commonly in the hip.

Causes and risk factors
Trauma, long‑term steroid use, alcohol use, and certain medical conditions.

Symptoms
Joint pain that worsens with weight‑bearing and progresses over time.

Diagnosis
MRI is most sensitive; X‑ray may be normal early.

Treatment
Early stages may respond to medications, reduced weight‑bearing, or core decompression. Advanced disease often requires joint replacement.

When to seek care
Persistent joint pain with risk factors warrants evaluation.