Posterolateral
Talus OCDs

The atypical corner of the talar dome — what does the literature actually say?

By Peter Sorensen, DPM

1The classic teaching

Every resident gets force-fed the DIAL a PIMP mnemonic — Berndt & Harty (1959) framework for talar OCD mechanism.

DIAL

D Dorsiflexion
I Inversion
A Anterolateral
L (Lateral lesion)

PIMP

P Plantarflexion
I Inversion
M (Medial side)
P Posteromedial

So the dogma: lateral OCDs sit anterolateral, medial OCDs sit posteromedial. Two corners. Clean. Memorable.

⚠ But wait... The mnemonic predates MRI. It comes from a cadaver study using ankle position to simulate impaction injury. It tells you a plausible mechanism — not the actual distribution seen in real patients.

2What MRI actually shows

Raikin, Elias et al. (2007) reviewed 428 talar OCDs on MRI and built the nine-zone grid that's now standard for talking about lesion location.

Raikin/Elias 9-zone grid. Zone 9 = posterolateral.

The actual frequencies:

        4
        Medial · mid (equator)
        53%
      

6 Lateral · mid (equator) 26%

7 Posteromedial (the "P" in PIMP) rare

3 Anterolateral (the "A" in DIAL) rare

9 Posterolateral rare

★ The plot twist Raikin found posteromedial AND anterolateral lesions were rare — most OCDs sit at the equator, not the corners. The DIAL/PIMP mnemonic captures the mechanism, not the modern epidemiology.

3Zone 9 — the forgotten corner

If anterolateral and posteromedial are uncommon, posterolateral is downright unusual. Most large series lump it into "lateral other" or "posterior other."

How rare? In January 2026, Kobai et al. published a Cureus case report on a posterolateral OLT treated open via a posterolateral approach — and explicitly noted no prior published reports of open posterolateral approach for these lesions.

↑ a 2026 case report... means we're still learning this corner

What we think we know about etiology:

Likely traumatic — most lateral talar OCDs (Berndt-Harty mechanism) are linked to inversion injury & chronic lateral ligamentous instability
May represent an atypical impaction pattern when dorsiflexion-inversion happens with the ankle in more plantarflexion than the classic anterolateral lesion
Some posterolateral lesions are likely missed on plain films and only show up on MRI for "post-traumatic ankle pain that won't resolve"

4The biomechanical paradox

Aslan et al. (2025) ran a finite element analysis on lesions across all 9 zones at 3 sizes (4.5, 6.4, 9 mm) in 3 ankle positions. Look at what they found for zone 9:

Δ ankle stiffness · 9 mm zone 9 defect

        Neutral: −4.7%

        Dorsiflexion: +5.4% (sic — within noise)

        Plantarflexion: +0.17%

Zone 9 was the least biomechanically critical zone in the entire grid. Compare to zone 8 (mid-posterior) at −48.8% stiffness with the same 9 mm defect.

So we have a paradox:

Posterolateral defects load less of the joint → potentially less symptomatic per mm of cartilage lost
But when patients DO present, the lesion is hardest to access surgically — classically requires fibular osteotomy
Treatment threshold may be higher than for zone 4/6, but options once you operate are more morbid

5Surgical access — the real problem

This is where posterolateral becomes a teaching case. Per Garras (2008) and Mayne (2016) cadaveric work, here's how much of the lateral talar dome you can perpendicular-access from each approach:

Anterolateral arthrotomy alone ~43%
+ ATFL release ~58%
Anterolateral tibial osteotomy ~68%
Fibular osteotomy (classical gold standard) 88–95%

↑ this is why posterolateral OCDs are scary to operate on

Where the field is moving:

Youn (2019): arthroscopic-assisted osteochondral allograft transfer for posterolateral lesions without fibular osteotomy
Sivasamy (2025): posterior ankle arthroscopy with prone positioning + dorsiflexion + iliac crest autograft — visualizes posterolateral lesion through the back door
Wang (2019): for retrograde drilling, the posterolateral approach causes less vascular damage than the anterolateral approach

6Decision lens

How surgeons think about zone 9:

Is this really zone 9, or is it a posterior zone 6 / posterior zone 8 misread on coronal MRI?

How big is the lesion? (Smaller subchondral lesions often tolerate non-perpendicular access)

Is there a cyst or bone loss? (If yes, you need a graft — and a graft needs perpendicular access)

Can posterior arthroscopy in prone position give you enough exposure? (Sivasamy / Takao technique)

If you must do the fibular osteotomy — are you ready for the syndesmotic risk, hardware, and potential nonunion?

7Pearls & pitfalls

"DIAL a PIMP" teaches mechanism, not modern distribution. Both can be true.
Zone 9 is the least biomechanically loaded zone — but still symptomatic when chondral integrity breaks down.
Posterior ankle arthroscopy (prone, posteromedial & posterolateral portals) is the access answer the field is converging on.
For retrograde drilling, posterolateral approach is more vascularly safe than anterolateral (Wang 2019).

Calling a posterior zone-6 lesion "posterolateral" — be precise on coronal AND axial MRI before you plan an approach.
Defaulting to fibular osteotomy without first asking whether a posterior arthroscopic approach would work.
Treating a small posterolateral defect aggressively because of where it is, when biomechanically it may tolerate observation or BMS.
Forgetting that posterolateral OLT often presents in the setting of chronic lateral instability — fix the ligament too.

Open vs. arthroscopic for posterolateral OLTs requiring grafting — no head-to-head trials
Allograft vs. iliac autograft for the cylindrical defect
Do we need posterolateral-specific outcome studies, or is "lateral OLT" a fair grouping for the literature?

Confidence level

6/10 — medium. Nine-zone distribution data (Raikin/Elias) is robust. Surgical-access cadaver data is robust. Specific posterolateral (zone 9) treatment outcomes are thin — mostly case reports and technique papers. ⚠ Verify locally before applying.

Sources

Raikin SM, Elias I, Zoga AC, et al. Osteochondral lesions of the talus: localization and morphologic data from 424 patients using a novel anatomical grid scheme. Foot Ankle Int. 2007;28(2):154-61. doi.org/10.3113/FAI.2007.0154
Aslan L, Subasi O, Karaismailoglu B, et al. In silico assessment of talus osteochondral lesion size and location on biomechanical load distribution using tilted talar dome planes. Acta Orthop Traumatol Turc. 2025;59(6):361-367. doi.org/10.5152/j.aott.2025.25444
Kobai Y, Sasaki T, Nakagawa Y, Yamada H. Open Reduction and Internal Fixation Using a Posterolateral Approach for a Posterolateral Osteochondral Lesion of the Talus: A Case Report. Cureus. 2026;18(1):e102542. doi.org/10.7759/cureus.102542
Sivasamy P, Miura T, Jujo Y, Takao M. Minimally Invasive Management of Posterolateral Osteochondral Lesions of the Talus Using Posterior Ankle Arthroscopy and Autologous Iliac Osteochondral Grafts. Arthrosc Tech. 2025;14(5):103458. doi.org/10.1016/j.eats.2025.103458
Youn GM, Rosinski A, Gwosdz J, et al. Arthroscopic-Assisted Osteochondral Allograft Transplantation for Posterolateral Lesions of the Talus Without Fibular Osteotomy. Arthrosc Tech. 2019;8(3):e311-e316. doi.org/10.1016/j.eats.2018.11.009
Garras DN, Santangelo JA, Wang DW, Easley ME. A quantitative comparison of surgical approaches for posterolateral osteochondral lesions of the talus. Foot Ankle Int. 2008;29(4):415-20. doi.org/10.3113/FAI.2008.0415
Mayne AIW, Lawton R, Reidy MJ, et al. A comparison of surgical exposures for posterolateral osteochondral lesions of the talar dome. Foot Ankle Surg. 2018;24(2):107-109. doi.org/10.1016/j.fas.2016.11.012
Wang D, Shen Z, Fang X, et al. Vascular Compromising Effect of Drilling for Osteochondral Lesions of the Talus: A 3D Micro-CT Study. Arthroscopy. 2019;35(10):2930-2937. doi.org/10.1016/j.arthro.2019.05.021
Sripanich Y, Dekeyser G, Steadman J, et al. Limitations of accessibility of the talar dome with different open surgical approaches. Knee Surg Sports Traumatol Arthrosc. 2021;29(4):1304-1317. doi.org/10.1007/s00167-020-06113-2

Literature retrieved via PubMed.

AI-assisted educational summary for podiatric residents and students. Not clinical advice, not for billing or coding, and not a substitute for institutional protocols, attending judgment, or current peer-reviewed practice guidelines. Verify all figures and recommendations against the primary literature before applying to patient care.

PosterolateralTalus OCDs