Avascular necrosis of the hip is a race against collapse — and timing is everything. A young patient with groin pain and a near-normal radiograph may already be heading toward femoral head failure. Identifying osteonecrosis on MRI before the crescent sign appears is the decision that determines whether you can preserve the native joint or commit the patient to decades of arthroplasty. This OrthoVellum lecture walks through femoral-head AVN from vascular anatomy and risk factors through Ficat, Steinberg, ARCO and Kerboul staging, real clinical imaging, and the treatment fork between core decompression, salvage, and total hip arthroplasty. ⏱ CHAPTERS 0:00 Intro 0:46 Chapter 1: Foundations 0:48 Catch AVN on MRI before subchondral collapse — once the crescent sign ap 1:58 One dominant vessel hugs the posterior neck — kink it, and the head dies 3:16 How the femoral head dies and collapses 4:59 Chapter 2: Recognising it 5:01 Insidious groin pain, painful internal rotation 6:23 Real MRI · bilateral femoral-head AVN · Kalekar et al., Cureus 2024 (CC 7:12 Real radiograph · bilateral femoral-head AVN · Bilge et al., JOSR (CC BY 7:54 Real radiograph · bilateral Stage III AVN · Kalekar et al., Cureus 2024 8:40 Chapter 3: Managing it 8:43 Is the head still spherical — and how old is the patient? 10:17 Inflection Points That Decide Joint Preservation 12:16 KEY NUMBERS 13:19 Take-home 14:44 Sources & disclaimer 🦴 KEY TAKEAWAYS • Catch AVN on MRI before subchondral collapse — joint preservation works in Ficat I–II. • The medial circumflex femoral artery and its posterosuperior retinacular branches leave the head vulnerable. • Image both hips: disease is bilateral in 50–80% within two years. • The crescent sign marks mechanical failure; after collapse, isolated decompression usually fails. • Stage with Ficat (when), Steinberg (how much), ARCO (where), and Kerboul angle (collapse risk). • Counsel young arthroplasty patients honestly about revision risk (~15–20% at 10 years). 🎨 CREDITS Original OrthoVellum educational production. Clinical images from attributed open-access sources (see video sources card). Narration: Kokoro TTS. Visual engine: OrthoVellum blend / HyperFrames lecture design. 🔗 More free orthopaedic teaching at Orthovellum.com — subscribe for weekly videos. ⚠️ Educational only — not individual medical advice. Always consult a qualified clinician for diagnosis and treatment. #avascularnecrosis #AVNhip #osteonecrosis #femoralhead #hippain #hippreservation #coredecompression #Ficatstaging #orthopaedics #orthopedics #hipsurgery #jointpreservation #medicaleducation #OrthoVellum