Synopsis
Recognise osteonecrosis before subchondral collapse, identify traumatic and systemic causes, use MRI when radiographs are unrevealing, protect the joint while staging is completed, and refer while joint-preserving options remain possible.
- Suspect femoral-head osteonecrosis in progressive groin or buttock pain with painful internal rotation, especially after glucocorticoids, heavy alcohol, trauma, sickle-cell disease, lupus or transplantation.
- Obtain anteroposterior pelvis and lateral hip radiographs first, while recognising that early osteonecrosis can be radiographically invisible.
- MRI without contrast is the preferred confirmatory test when suspicion persists and sensitively defines lesion location, size, bilateral disease and early subchondral fracture.
- A crescent sign represents subchondral fracture; femoral-head flattening and joint-space change indicate collapse and secondary arthritis.
- Refer promptly to hip-preservation or orthopaedic care before collapse; core decompression, sometimes with graft or augmentation, is considered for selected symptomatic early lesions.
- After collapse, joint-preserving procedures are less predictable and total hip replacement usually provides the most reliable definitive relief for advanced symptomatic disease.
- Reduce modifiable exposure but never stop long-term glucocorticoids abruptly; coordinate the lowest effective dose or steroid-sparing treatment with the responsible team.
- No established routine medicine reverses osteonecrosis; analgesia and protected loading control symptoms while stage-specific surgical decisions are made.
Key red flags
A shortened or rotated limb, major trauma or sudden inability to bear weight requires urgent exclusion of femoral-neck fracture or hip dislocation.
Fever, marked warmth, severe pain with passive movement or immunosuppression requires urgent aspiration and treatment planning for septic arthritis.
Night pain, weight loss, a mass, cytopenias or a destructive lesion suggests malignancy, infection or marrow disease rather than isolated osteonecrosis.
New bilateral hip pain during high-dose glucocorticoids, after transplantation or with sickle-cell disease merits early MRI because symptoms can precede radiographic change.
Investigation priorities
Exclude fracture, advanced osteoarthritis and destruction while identifying sclerosis, cysts, crescent fracture or flattening.
Detect early necrotic bone, define lesion size and weight-bearing location, assess subchondral integrity and examine both hips.
Management branches
Groin or joint pain and restricted movement occur after a recognised vascular insult or systemic exposure.
- Exclude fracture, dislocation and septic arthritis from acuity, observations and examination, then document glucocorticoid, alcohol, trauma, haematological and systemic risks.
- Obtain orthogonal radiographs and proceed to MRI of both hips when films are normal or equivocal but clinical probability remains meaningful.
- Stage by collapse, size and load-bearing location, assess other high-risk joints and refer before advising prolonged observation.
- Provide a walking aid, adapt high-impact loading and maintain safe conditioning while diagnosis and surgical strategy are completed.