High-yield overview
4 stagesI–IV by fragment detachment and displacement
Stage I–IInon-operative — immobilisation and non-weight-bearing
Stage IIIgrey zone — fixation if viable, excision if not
Stage IVarthroscopic excision plus microfracture or OATS
Critical Must-Knows
- Berndt-Harty classifies osteochondral lesions of the talus (OLTs) by the degree of fragment detachment and displacement, guiding the transition from conservative to operative management.
- Stage I is subchondral compression with intact cartilage; Stage II is a partially detached fragment; Stage III is completely detached but still in the crater; Stage IV is completely detached and displaced as a loose body.
- Medial lesions are more common, deeper, cup-shaped and posteromedial — typically from inversion plus dorsiflexion plus external rotation. Lateral lesions are shallower, wafer-shaped and anterolateral — typically from inversion plus dorsiflexion plus talar tilt producing a shearing force.
- Non-operative management is first-line for Stage I and II (6 weeks non-weight-bearing). Stage IV loose bodies always require operative removal with microfracture of the base. Stage III is the decision point: if the fragment is acute and viable, fix it; if chronic or sclerotic, excise and microfracture.
The staging examiners want
The Berndt-Harty stage directly guides management: Stage I–II are managed conservatively; Stage III is the grey zone — examiners expect you to discuss both fixation of a viable fragment and excision with microfracture, justifying your choice based on fragment viability, chronicity, and size. Stage IV always requires surgery — a displaced loose body will not heal. Always mention MRI staging (Hepple modification) alongside the plain-film classification, because plain radiographs underestimate lesion severity in a significant proportion of cases.
The Berndt-Harty Classification
The classification is based on radiographic and arthroscopic assessment of the osteochondral fragment at the talar dome.
| Stage | Pathology | Radiographic Finding | Cartilage Status |
|---|---|---|---|
| I | Subchondral compression | Compression of subchondral bone, no visible fragment | Intact |
| II | Partially detached fragment | Fragment partly separated from the talar dome | Partially breached |
| III | Completely detached, not displaced | Fragment separated but still within the crater | Completely breached |
| IV | Completely detached and displaced | Fragment displaced from crater — loose body in joint | Disrupted with loose body |
Mnemonic
C P D D — Compressed, Partial, Detached, DisplacedThe four stages
Mnemonic
MPAL — Medial = Posterior, cup-shaped; Lateral = Anterior, wafer-shapedMedial versus lateral lesion patterns
Mnemonic
NCFF — Non-op, Conservative trial, Fix if viable, Free fragment outManagement by stage
Clinical Pearl
Medial lesions are deep and cup-shaped; lateral lesions are shallow and wafer-shaped. This matters because shallow lateral lesions are harder to fix (less bone stock for fixation devices) and more often require excision. Deep medial lesions have better bone stock for biologic fixation when caught before displacement.
MRI Staging and Management Algorithm
The Hepple modification extends Berndt-Harty for MRI, adding sub-stages and a cyst stage that refine management decisions.
| MRI Stage | Finding on MRI | Berndt-Harty Equivalent | Management Implication |
|---|---|---|---|
| 1 | Cartilage thickening, low signal, no fracture line | I | Non-operative |
| 2a | Cartilage breach, underlying fracture, bony oedema present | I–II | Non-operative trial; early arthroscopy if failing |
| 2b | Cartilage breach, underlying fracture, no bony oedema | II | Arthroscopy likely — fragment may be unstable |
| 3 | Detached but undisplaced fragment in crater | III | Fix if viable; excise and microfracture if not |
| 4 | Displaced fragment — loose body | IV | Arthroscopic excision plus microfracture or OATS |
| 5 | Subchondral cyst, intact or breached cartilage | Late-stage | Cyst management plus cartilage restoration |
Caution
Do not rely on plain radiographs alone to stage an OLT. MRI is essential — it reveals cartilage integrity, fragment stability, bony oedema, and subchondral cysts invisible on plain films. CT is useful for surgical planning (mapping fragment size, location, and bone stock) but does not assess cartilage or marrow oedema. A lesion that looks like Stage I on X-ray may be Stage III or higher on MRI.
Limitations and Modern Context
- The original classification is based on plain radiographs and surgical observation from 1959. MRI staging (Hepple 1999) adds precision, but the Berndt-Harty framework remains the universal language for examiners and surgeons.
- Stage III is inherently subjective. Whether a completely detached fragment is truly in situ or has begun to shift depends on imaging quality, timing, and the interval between injury and scanning. Intra-operative assessment frequently upstages the pre-operative classification.
- Chronicity matters more than stage alone. An acute Stage III lesion with viable, bleeding subchondral bone is a fixation candidate. A chronic Stage III lesion with sclerotic margins and cystic degeneration is better served by excision and cartilage restoration (microfracture, OATS, or autologous osteochondral transplantation).
- Lesion size is not part of Berndt-Harty but critically affects outcomes. Lesions greater than 15 mm in diameter or greater than 150 mm squared in area have worse outcomes with microfracture alone and are more appropriate for OATS or osteochondral allograft.
- Newer techniques — matrix-associated autologous chondrocyte implantation (MACI), particulated juvenile cartilage (DeNovo NT), and hyaluronic acid-based scaffolds — are expanding the options for larger or failed lesions but remain beyond the basic classification framework examiners test.
- Berndt-Harty applies to the talar dome only. Osteochondral lesions of the tibial plafond, navicular, or other tarsal bones are not classified by this system.
Evidence Base
Evidence
Transchondral fractures (osteochondritis dissecans) of the talus
Berndt AL, Harty M • J Bone Joint Surg Am (1959)
Key Findings:
- Original four-stage classification derived from cadaveric experiments and clinical cases
- Stage I subchondral compression through Stage IV displaced loose body
- Described distinct mechanisms: medial lesions from inversion-dorsiflexion-external rotation; lateral from inversion-dorsiflexion-talar tilt
Clinical implication: Established the universally adopted staging system that remains the basis for OLT management worldwide.
Limitation: Small case series; cadaveric biomechanical model; pre-MRI and pre-arthroscopy era.
Source: J Bone Joint Surg Am 1959;41-A:988-1020
Evidence
Osteochondral lesions of the talus: a revised classification
Hepple S, Winson IG, Glew D • Foot Ankle Int (1999)
Key Findings:
- Extended Berndt-Harty to six MRI stages, adding subchondral cyst formation and oedema sub-staging
- MRI detected lesions not visible on plain radiographs in a substantial proportion of patients
- Presence or absence of bony oedema (Stage 2a versus 2b) correlated with lesion instability
Clinical implication: Provided the MRI staging framework now used alongside Berndt-Harty for pre-operative planning and prognostication.
Limitation: Retrospective; limited correlation with arthroscopic findings in all patients.
Source: Foot Ankle Int 1999;20(12):789-93
Evidence
Arthroscopic treatment of chronic osteochondral lesions of the talus: long-term results
Ferkel RD, Zanotti RM, Komenda GA, et al. • Am J Sports Med (2008)
Key Findings:
- Large arthroscopic series with good to excellent outcomes in the majority of patients after excision and microfracture for Stage III–IV lesions
- Cystic lesions and lesions greater than 15 mm had inferior outcomes after microfracture alone
- Medial lesions had better outcomes than lateral lesions after arthroscopic management
Clinical implication: Supported arthroscopic excision with microfracture as the gold standard for displaced and non-viable OLTs.
Limitation: Retrospective; heterogeneous techniques; no control group.
Source: Am J Sports Med 2008;36(9):1750-62
Evidence
Treatment of osteochondral lesions of the talus: a systematic review
Zengerink M, Struijs PAA, Tol JL, van Dijk CN • Knee Surg Sports Traumatol Arthrosc (2010)
Key Findings:
- Stage I–II lesions respond to conservative management in approximately 50 to 70 percent of patients
- Bone marrow stimulation (microfracture or drilling) produced good results for lesions up to 15 mm
- Larger and cystic lesions had better outcomes with OATS than microfracture alone
Clinical implication: Established the 15 mm size threshold as the key decision point between microfracture and osteochondral grafting.
Limitation: Heterogeneous primary studies; variable follow-up durations; few randomised trials.
Source: Knee Surg Sports Traumatol Arthrosc 2010;18(2):238-46
Exam Viva
Practise clinical reasoning and management decisions out loud
Viva scenarioStandard
Clinical prompt
“A 28-year-old netballer presents with persistent right ankle pain six months after an inversion injury. MRI shows a 10 mm osteochondral lesion on the posteromedial talar dome with a completely detached but undisplaced fragment. How would you classify and manage this?”
Practical approach
This is a Berndt-Harty Stage III osteochondral lesion of the talus — completely detached but not displaced. On the Hepple MRI staging it is Stage 3. The lesion is medial (the more common location), 10 mm in diameter, and cup-shaped. Given the six-month history of failure of conservative management and the detached fragment, I would recommend diagnostic arthroscopy. If the fragment has healthy bleeding subchondral bone and the crater bed is viable, I would fix it with bioabsorbable pins or headless compression screws. If the fragment is sclerotic, cystic, or non-viable, I would excise it and perform microfracture of the base. Post-operatively the patient would be non-weight-bearing for 6 weeks with early range-of-motion exercises. Return to sport would be anticipated at 4 to 6 months. I would counsel her that the outcome depends on fragment viability and lesion size, and that larger or cystic lesions have a higher failure rate.
Key clinical points
State the Berndt-Harty stage explicitly (Stage III) and MRI stage (Hepple 3)
10 mm lesion is within the size range for microfracture or fixation
Decision hinges on fragment viability assessed at arthroscopy
Medial lesion — cup-shaped, better bone stock for fixation than lateral
Common pitfalls
Calling it Stage IV — it is not displaced, the fragment remains in the crater
Recommending continued non-operative management after six months of failure
Not discussing both fixation and excision options for Stage III
Further questions
“How would management change if the fragment were displaced (Stage IV)?”
“What if the lesion were 20 mm — does that change your operative plan?”
“What is the role of OATS in this patient?”
Viva scenarioAdvanced
Clinical prompt
“A 35-year-old runner had arthroscopic excision and microfracture of a lateral talar OLT (Berndt-Harty Stage IV, 12 mm) two years ago. She now has recurrent pain and new MRI shows a subchondral cyst at the same site with intact overlying cartilage. How do you classify this, and what is the management?”
Practical approach
This is a failed microfracture with development of a subchondral cyst — Hepple MRI Stage 5. The intact overlying cartilage on MRI suggests the cyst is contained, but the biomechanical environment is compromised and the cyst will likely enlarge without intervention. I would obtain a CT scan to define the cyst dimensions precisely and confirm cartilage integrity, as MRI can overcall intact cartilage. Management options include retrograde drilling and bone grafting of the cyst (if cartilage is truly intact), or if the cartilage is breached, osteochondral autologous transfer (OATS) from the ipsilateral knee to replace both bone and cartilage in a single stage. Matrix-associated autologous chondrocyte implantation (MACI) is an alternative but requires two stages. Given her high functional demands as a runner and a 12 mm lesion, I would favour OATS for single-stage biologic reconstruction. Post-operatively she would be non-weight-bearing for 6 weeks with passive motion only, and return to running would not be before 6 months. I would counsel her that OATS has good mid-term outcomes but donor-site knee morbidity is a recognised consideration.
Key clinical points
Recognise Hepple Stage 5 — subchondral cyst complicating prior microfracture
Obtain CT for surgical planning to map cyst dimensions and confirm cartilage status
OATS for a 12 mm lesion with subchondral bone loss addresses both bone and cartilage
Discuss donor-site morbidity and the staged versus single-stage surgical options
Common pitfalls
Repeating microfracture for a cystic lesion — success rates are low in revision settings
Not obtaining CT before operative planning
Assuming intact cartilage on MRI means no intervention is needed — the cyst will enlarge
Further questions
“What is the evidence for OATS versus ACI in talar OLTs?”
“How do you manage donor-site morbidity from the knee for OATS?”
“What is the role of particulated juvenile cartilage in this scenario?”
Exam day cheat sheet
Berndt-Harty Classification — Exam Cheat Sheet
The four stages
- Stage I: subchondral compression — cartilage intact, no visible fragment
- Stage II: partial detachment — fragment partly separated from the dome
- Stage III: complete detachment, fragment still in crater (not displaced)
- Stage IV: complete detachment with displacement — loose body in the joint
Medial versus lateral patterns
- Medial (about 60 percent): posteromedial, cup-shaped, deep — inversion + dorsiflexion + external rotation
- Lateral (about 40 percent): anterolateral, wafer-shaped, shallow — inversion + dorsiflexion + talar tilt (shearing)
- Lateral lesions are more often symptomatic and more likely to become loose bodies
- Medial lesions have better bone stock for fixation when caught before displacement
Management by stage and size
- Stage I–II: non-weight-bearing cast or boot for 6 weeks; arthroscopy if failing at 3 months
- Stage III: fix if viable (acute, good bone); excise and microfracture if chronic or non-viable
- Stage IV: arthroscopic excision of loose body plus microfracture; OATS if greater than 15 mm
- Size threshold: microfracture for up to 15 mm; OATS or ACI for larger lesions
Key pitfalls
- Always get MRI — plain films underestimate stage in up to half of cases
- Stage III is the examiner's grey zone: discuss both fixation and excision with justification
- Chronicity and cystic change push toward excision and cartilage restoration, not fixation
- Hepple Stage 5 (subchondral cyst) requires bone grafting or OATS, not just microfracture