Inflammatory arthritis (e.g., rheumatoid arthritis, lupus): This is a common condition that can cause joint pain and inflammation, and the symptoms can sometimes mimic those of osteonecrosis.
Osteonecrosis of the femoral head: This condition, also known as avascular necrosis, occurs when the blood supply to the femoral head is disrupted, leading to bone death and potentially severe pain.

Osteoarthritis: A degenerative joint disease that can cause pain and stiffness in the hip, which may be confused with inflammatory arthritis or osteonecrosis.
Transient osteoporosis of the hip: A condition characterized by temporary bone loss in the hip, often causing pain and mimicking other hip conditions.
Septic arthritis: An infection within the joint, which can cause severe pain, swelling, and inflammation, and may be mistaken for inflammatory arthritis.

Septic arthritis: Although mentioned earlier, it's crucial to emphasize that missing this diagnosis can lead to severe joint destruction and systemic infection.
Fracture: A hip fracture can present with similar symptoms to osteonecrosis or inflammatory arthritis, especially in older adults or those with osteoporosis.
Malignancy: Bone tumors, such as osteosarcoma or metastatic disease, can cause hip pain and may be overlooked if not considered in the differential diagnosis.

Legg-Calve-Perthes disease: A rare condition in children where the blood supply to the femoral head is disrupted, leading to osteonecrosis.
Gaucher's disease: A genetic disorder that can cause osteonecrosis due to the accumulation of harmful substances within cells.
Caisson disease (decompression sickness): A rare condition that occurs when gas bubbles form in the bloodstream and tissues, potentially causing osteonecrosis.