Optimizing diagnosis and management of ONFH, FNSF, and SIF.

Osteonecrosis of the femoral head (ONFH), femoral neck stress fracture (FNSF), and subchondral insufficiency fracture (SIF) are distinct yet clinically overlapping causes of non-arthritic hip pain. All three conditions threaten femoral head viability via distinct pathophysiologic mechanisms and may lead to fracture displacement (FNSF) and irreversible collapse (ONFH, SIF, and displaced FNSF), ultimately necessitating arthroplasty if not identified and managed early. These conditions frequently present with groin pain and unremarkable radiographs in their early stages. Imaging may be normal or show generalized bone marrow edema. MRI is the most sensitive modality for detection; however, accurate diagnosis requires the integration of specific imaging features with the synthesis of the patient's past medical history, including age, activity level, and bone quality. ONFH identified before collapse may be amenable to joint-preserving procedures, such as core decompression. FNSF requires urgent recognition and non-weight-bearing precautions to avoid displacement and vascular injury. SIF may be managed conservatively with protected weight-bearing and monitoring. Despite the expertise of experienced examiners and advanced imaging techniques, the initial diagnosis is frequently incorrect, and treatment options only become clear with timely follow-up and serial imaging. This review highlights diagnostic distinctions among ONFH, FNSF, and SIF, emphasizing clinical context, imaging-based differentiation, and appropriate management. Accurate early classification is crucial for guiding management decisions and preventing collapse of the femoral head or femoral neck displacement.