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Nontraumatic osteonecrosis of the femoral head — MSRA MCQ

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HardHip and GroinNontraumatic osteonecrosis of the femoral headMSRA

A 38-year-old man presents with a 7-week history of progressive right deep groin pain. It is now painful at rest and wakes him when turning in bed. Walking aggravates the pain and he has started using a stick. Three months ago, he completed a 6-week reducing course of prednisolone, initially 60 mg daily, for immune thrombocytopenia. He has no history of trauma, fever, weight loss, back pain or alcohol excess. Examination shows an antalgic gait and pain with passive internal rotation of the right hip. There is no erythema, warmth or focal bony tenderness. Full blood count, CRP and ESR are normal. An anteroposterior pelvic radiograph taken 10 days ago was reported as normal. What is the most appropriate next investigation?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — MRI scan of the right hip

Explanation lettering: B = shown as A · E = shown as B · A = shown as E

This presentation should raise suspicion of femoral-head osteonecrosis. The discriminating features are deep groin pain arising in a relatively young adult, progression to rest/night pain with painful hip rotation, and recent high-dose systemic glucocorticoid exposure. Normal inflammatory markers make septic arthritis or an inflammatory arthropathy less likely, while the absence of trauma does not explain the severity of symptoms. A normal plain radiograph does not exclude early osteonecrosis: radiographic changes may appear only after established structural disease. MRI is the most sensitive and specific imaging modality for osteonecrosis of the femoral head and identifies early marrow and subchondral abnormalities before radiographic collapse. It also helps define lesion extent, which influences specialist management. A is inappropriate because delaying investigation risks missing potentially joint-preserving early disease. B may detect subchondral collapse but is less useful than MRI for early osteonecrosis. D can detect altered bone turnover but is less accurate and is not the preferred test when MRI is available. E may identify an effusion or superficial peri-articular pathology, but cannot reliably assess femoral-head osteonecrosis.

Reference: Diagnosis and Treatment of Nontraumatic Osteonecrosis of the Femoral Head: A Systematic Review and Meta-Analyses for the ARCO Clinical Practice Guideline Development Workgroup (2026) — https://pubmed.ncbi.nlm.nih.gov/41892822/ ACR Appropriateness Criteria Osteonecrosis of the Hip (2016) — https://pubmed.ncbi.nlm.nih.gov/26846390/