# ARCO — 2019 revised ARCO staging of osteonecrosis of the femoral head

> Per-hip stage I-IV framework for nontraumatic osteonecrosis of the femoral head. A subchondral or necrotic-zone fracture is the decisive stage-II/III boundary; lesion size and location, symptoms, age and patient goals remain separate inputs and must not be inferred from the stage.

**Situação:** vigente · **Órgão:** Musculoesquelético · **Órgão emissor:** Association Research Circulation Osseous · **Versão:** 2019 revised staging; 2026 ARCO/AAOS care context · **Ano:** 2019

> ⚠️ Uma versão mais nova pode existir (em revisão).

## Procedência e vigência
- Família: léxico
- Tipo de lógica: flat
- Modalidade: MRI, XR, CT
- Fonte primária: Yoon BH, Mont MA, Koo KH, et al.. The 2019 Revised Version of Association Research Circulation Osseous Staging System of Osteonecrosis of the Femoral Head (2020) — https://pubmed.ncbi.nlm.nih.gov/31866252/
- Última verificação: 2026-07-24
- Última checagem: 2026-08-12

## Lógica de decisão
Stage each hip from the highest directly supported structural finding. Fracture is the stage-II/III boundary; lesion size, location, symptoms and treatment choice remain explicit separate inputs.

## Categorias

| Código | Rótulo | Critérios | Conduta | Risco | Localizador | Verificado |
| --- | --- | --- | --- | --- | --- | --- |
| 1 | Grade 1 | 2019 revised ARCO stage I is a hip with normal radiographs but osteonecrosis demonstrated by a band-like low-signal lesion on T1-weighted MRI and/or a positive bone scan. There is no subchondral or necrotic-zone fracture, femoral-head depression or secondary osteoarthritis. Stage each hip independently and do not emit the deleted historical stage 0 for an imaging-negative hip. | MRI is the preferred diagnostic test. For an asymptomatic or symptomatic pre-fracture hip, discuss observation versus joint-preserving intervention using symptoms, lesion size and location, age and patient goals. The 2026 ARCO guideline allows consideration of core decompression and selected augmentation but does not establish one universally superior intervention or authorize a stage-I-only treatment command. | Stage I is structurally pre-fracture, but the stage supplies no calibrated individual probability of collapse. Lesion size and weight-bearing location are major separate determinants, so two stage-I hips can have materially different risk. Record the named size/location method, symptoms, etiology and serial imaging instead of assigning a stage-only percentage. | Yoon et al. J Arthroplasty 2020, DOI 10.1016/j.arth.2019.11.029, 2019 revised ARCO staging table and revision rationale; Cheng et al. JBJS 2026, DOI 10.2106/JBJS.25.01616, Recommendations on diagnostic MRI, asymptomatic stage I-II and core decompression; ARCO update review PMC8216992, 2019 staging and separate size/location systems. | ✓ |
| 2 | Grade 2 | 2019 revised ARCO stage II has radiographic osteonecrosis such as sclerosis, focal osteoporosis or cystic change, but no subchondral or necrotic-zone fracture, no femoral-head flattening or depression and no secondary osteoarthritis. If fracture status is unresolved, especially on radiography alone, retain stage II versus III uncertainty and use CT or appropriate MRI review rather than assuming stage II. | For stage II without fracture, use shared decision-making informed by pain, function, lesion size and location, age, etiology and expected lifespan. Core decompression with or without bone-marrow-cell augmentation and selected vascularized grafting or osteotomy may be considered, but evidence is weak or low and does not support an automatic procedure. CT can be important when an occult fracture would change the stage and counseling. | Stage II remains pre-fracture but is not a uniform collapse-risk group. Extent and location are intentionally outside the 2019 stage and strongly modify risk; the stage paper provides no portable per-stage probability. A reported stage II should therefore include fracture-detection adequacy and a separate lesion-extent descriptor. | Yoon et al. 2020 primary revised staging table, stage II and deleted size/location subclasses; Cheng et al. 2026 guideline, diagnostic CT/MRI for subchondral fracture and stage I-II joint-preservation recommendations; PMC8216992, size/location as major collapse determinants distinct from ARCO stage. | ✓ |
| 3 | Grade 3 | 2019 revised ARCO stage III requires a subchondral or necrotic-zone fracture on radiography or CT, with or without visible collapse. Measure maximum femoral-head depression: IIIA is 2 mm or less, including exactly 2 mm, and IIIB is more than 2 mm. A fracture is sufficient for stage III before flattening; collapse without secondary osteoarthritis remains stage III rather than IV. | After fracture or collapse, compare the smaller and less predictable functional benefit of joint preservation with total hip arthroplasty through shared decision-making, particularly in younger patients. Age, remaining lifespan, depression, lesion size/location, symptoms, function and preferences are required. Stage III does not autonomously select grafting, osteotomy or arthroplasty, and IIIA versus IIIB is not a stand-alone procedure rule. | Stage III demonstrates structural failure and generally carries greater progression and arthroplasty concern than pre-fracture stages, but neither IIIA nor IIIB has a universal individual outcome percentage in the staging system. Depression, extent, location, symptoms and patient factors remain necessary, and serial exams must preserve the date at which fracture or collapse first became visible. | Yoon et al. 2020 primary revised staging table, stage III fracture criterion and 2 mm IIIA/IIIB boundary; Cheng et al. 2026 guideline, stage-III joint-preservation versus total-hip-arthroplasty counseling and age, lesion-size and patient-value context. | ✓ |
| 4 | Grade 4 | 2019 revised ARCO stage IV is secondary osteoarthritis on radiography, with joint-space narrowing, acetabular change and/or joint destruction after femoral-head osteonecrosis and collapse. Collapse alone is insufficient; verify an osteoarthritic joint or acetabular feature before moving a hip from stage III to IV. | Secondary osteoarthritis commonly makes total hip arthroplasty an important option, but management still depends on pain, disability, age, comorbidity, prior preservation procedures and patient goals. The stage must not be converted into an automatic arthroplasty order, and the contralateral hip requires its own independent stage and care plan. | Stage IV represents the most advanced structural category and established secondary joint degeneration, not a calibrated probability of pain, disability, surgical candidacy or implant outcome. Report function, symptoms, joint destruction, bone stock and patient context rather than treating the numeral as an individual prognosis. | Yoon et al. 2020 primary revised staging table, stage-IV joint-space, acetabular and joint-destruction criteria; Cheng et al. 2026 evidence-based guideline, treatment framework and shared-decision boundary for advanced nontraumatic osteonecrosis. | ✓ |

### Citações por categoria
- **1**: Yoon BH, Mont MA, Koo KH, et al.. The 2019 Revised Version of Association Research Circulation Osseous Staging System of Osteonecrosis of the Femoral Head (2020) — https://pubmed.ncbi.nlm.nih.gov/31866252/ · Yoon et al. J Arthroplasty 2020, DOI 10.1016/j.arth.2019.11.029, 2019 revised ARCO staging table and revision rationale; Cheng et al. JBJS 2026, DOI 10.2106/JBJS.25.01616, Recommendations on diagnostic MRI, asymptomatic stage I-II and core decompression; ARCO update review PMC8216992, 2019 staging and separate size/location systems.
- **2**: Yoon BH, Mont MA, Koo KH, et al.. The 2019 Revised Version of Association Research Circulation Osseous Staging System of Osteonecrosis of the Femoral Head (2020) — https://pubmed.ncbi.nlm.nih.gov/31866252/ · Yoon et al. 2020 primary revised staging table, stage II and deleted size/location subclasses; Cheng et al. 2026 guideline, diagnostic CT/MRI for subchondral fracture and stage I-II joint-preservation recommendations; PMC8216992, size/location as major collapse determinants distinct from ARCO stage.
- **3**: Yoon BH, Mont MA, Koo KH, et al.. The 2019 Revised Version of Association Research Circulation Osseous Staging System of Osteonecrosis of the Femoral Head (2020) — https://pubmed.ncbi.nlm.nih.gov/31866252/ · Yoon et al. 2020 primary revised staging table, stage III fracture criterion and 2 mm IIIA/IIIB boundary; Cheng et al. 2026 guideline, stage-III joint-preservation versus total-hip-arthroplasty counseling and age, lesion-size and patient-value context.
- **4**: Yoon BH, Mont MA, Koo KH, et al.. The 2019 Revised Version of Association Research Circulation Osseous Staging System of Osteonecrosis of the Femoral Head (2020) — https://pubmed.ncbi.nlm.nih.gov/31866252/ · Yoon et al. 2020 primary revised staging table, stage-IV joint-space, acetabular and joint-destruction criteria; Cheng et al. 2026 evidence-based guideline, treatment framework and shared-decision boundary for advanced nontraumatic osteonecrosis.

## Histórico de versões

| Data | Evento | Detalhe | Situação |
| --- | --- | --- | --- |
| 2026-07-25 | revised | Monitored source changed (content_hash). Detected automatically; awaiting reviewer confirmation. | needs_review |
| 2026-01-20 | revised | ARCO adopted an international evidence-based clinical practice guideline for nontraumatic femoral-head osteonecrosis. It supplies current imaging and care context without changing the 2019 stage codes. | confirmed |
| 2019-12-24 | revised | ARCO published its 2019 revised staging: historical stage 0 was deleted, stage III was split at 2 mm of femoral-head depression, and prior size/location subclasses were left outside the I-IV stage. | confirmed |
| 2019-06-01 | revised | ARCO classification revised (2019). | confirmed |


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