Talar Osteochondral Lesion

The classic story is a young, active adult with an inversion ankle injury six to twelve months ago whose ankle has never been right since. Pain is typically deep, poorly localised, worse with weight-bearing, and worse with impact sports. Mechanical symptoms (catching, clicking, giving way, occasional true locking) suggest fragment instability or a loose body and warrant early imaging.

Examination findings are often subtle:

• •Look for an effusion
• •Tenderness over the anteromedial or anterolateral talar dome with the foot plantarflexed (which exposes the talar dome anterior to the tibial plafond)
• •Range of motion typically normal or mildly reduced
• •Anterior drawer and talar tilt may be positive if there is concomitant lateral ligament insufficiency, which is common

Red flags suggesting urgent imaging and specialist referral: true mechanical locking; suspected or imaging-confirmed intra-articular loose body; displaced fragment; progressive functional decline despite adequate rest. Persistent post-sprain ankle pain beyond 6 to 8 weeks should prompt MRI - failing to do so is a common cause of delayed diagnosis.

Key differentials include anterior ankle impingement (pain reproduced specifically at end-range dorsiflexion, anterior tibial and talar osteophytes on X-ray), posterior ankle impingement (forced plantarflexion, often with an os trigonum in dancers and footballers), chronic lateral ankle instability (which frequently coexists with OLT), and early ankle osteoarthritis.

Plain radiographs (standing AP, mortise, and lateral views) are first-line but have low sensitivity (around 40 percent); approximately 30 to 50 percent of OLTs are missed on initial plain films. The threshold for MRI in persistent post-sprain ankle pain should therefore be low.

MRI is the gold-standard imaging investigation, with sensitivity and specificity around 96 percent for cartilage integrity, bone marrow oedema, lesion stability, and subchondral cysts.

CT is complementary (sensitivity around 81 percent, specificity around 99 percent); it is superior for bony architecture, cyst size measurement, and surgical planning.

Two classifications come up repeatedly in exams:

• •Berndt and Harty (1959), radiographic, four stages: I subchondral compression, II partial detachment, III complete detachment without displacement, IV displaced fragment
• •Hepple MRI classification, which adds stage V for subchondral cyst formation. Clinically important because a cyst with intact overlying cartilage has specific surgical implications (typically retrograde drilling rather than microfracture)

Always assess for concomitant chronic lateral ankle instability, syndesmotic pathology, cavovarus or other malalignment, and degenerative change - these influence treatment and prognosis.

Initial non-operative management is reasonable for small, stable, non-displaced lesions without loose bodies: relative rest and activity modification; a period of immobilisation in a walking boot or below-knee cast where symptoms warrant; simple analgesia; structured physiotherapy focused on proprioception and lateral ligament rehabilitation. Outcomes are unpredictable, the optimal protocol is not firmly established, and fewer than half of patients achieve durable success in some series. Juvenile OCD with open physes has a notably better response to strict immobilisation and warrants a longer conservative trial.

Surgical referral indications: unstable lesions (Berndt and Harty III/IV, Hepple III to V); persistent symptoms despite optimised conservative care; mechanical symptoms or imaging-confirmed loose body; large or cystic lesions. Refer to a foot and ankle surgeon.

Acute displaced osteochondral fragments may require urgent arthroscopy. Large viable fragments should be reduced and fixed where possible; smaller or devitalised fragments are usually excised with curettage and bone marrow stimulation of the lesion base.

Surgical technique is driven by lesion size and morphology:

• •Small lesions (under approximately 100 to 150 mm sq): arthroscopic bone marrow stimulation (microfracture or drilling). The standard first-line surgical option
• •Subchondral cyst with intact cartilage cap: retrograde drilling, often with bone graft. Microfracture would needlessly breach intact cartilage
• •Larger or revision lesions: osteochondral autograft transfer (OAT), allograft, or AMIC (autologous matrix-induced chondrogenesis) under specialist care

Modern UK practice favours AMIC as a single-stage option for mid-to-large lesions. NHS England does not routinely commission autologous chondrocyte implantation (ACI/MACI) for osteochondral lesions of the talus in adults, on the basis that evidence was considered insufficient for routine commissioning; MACI is therefore reserved for selected specialist contexts. UK specialist practice for talar OLTs aligns with BOFAS guidance.

Concomitant chronic lateral ankle instability, cavovarus or other malalignment, syndesmotic pathology, and degenerative change should be assessed and corrected before or during OLT surgery where clinically relevant, because untreated abnormal loading worsens prognosis.

Post-operative rehabilitation is procedure-specific but follows a predictable arc.

After bone marrow stimulation: non-weight-bearing for around 6 weeks to allow the fibrocartilage clot to mature; early range of motion to prevent stiffness; progressive weight-bearing follows; return to running at 3 to 4 months; return to cutting and pivoting sports at 6 to 9 months.

After OAT, MACI, or AMIC: timeline is longer (return to sport often 9 to 12 months); protected weight-bearing is more cautious.

Patients should be counselled that recovery is measured in months not weeks, that swelling after activity may persist for up to a year, and that the goal is durable function rather than perfection.

For the conservatively managed patient, rehabilitation centres on calf and peroneal strengthening, single-leg balance, proprioceptive retraining, and a graduated return to impact loading guided by symptoms. Where chronic lateral ankle instability coexists, structured proprioceptive and peroneal strengthening (the same programme as for chronic ankle instability) is essential to protect the joint and reduce recurrence.

• •BOFAS Hyperbook: Talar Osteochondral Lesions - UK specialist consensus on diagnosis, classification, and surgical pathway including AMIC for mid-to-large lesions.
• •Berndt and Harty (JBJS-Am 1959) - the original four-stage radiographic classification of transchondral talar fractures; still the most commonly tested classification.
• •Hepple et al. (Foot Ankle Int 1999) - MRI classification adding stage V for subchondral cyst formation, which has specific implications for retrograde drilling versus microfracture.
• •NHS England Clinical Commissioning Policy - ACI/MACI is not routinely commissioned for osteochondral lesions of the talus in adults; MACI is reserved for selected specialist contexts.
• •BJSM consensus on chronic ankle instability - concomitant lateral ligament insufficiency must be assessed and addressed before or during OLT surgery.

• •The DipMSK loves the medial-versus-lateral lesion distinction; learn it cold using DIAL a PIMP. Lateral lesions are anterolateral, shallow, wafer-shaped, and almost always traumatic. Medial lesions are posteromedial, deeper, cup-shaped, and more often cystic.
• •Avoid stating that lateral lesions universally behave worse - prognosis depends on size, containment, cystic change, chronicity, and biomechanical drivers.
• •Young patient with persistent ankle pain after a sprain plus mechanical symptoms = OLT until proven otherwise.
• •Subchondral cyst with intact cartilage cap on MRI = retrograde drilling (with or without bone graft) is the high-yield surgical answer; microfracture would needlessly breach intact cartilage.
• •Plain X-rays miss 30 to 50 percent of OLTs; threshold for MRI in persistent post-sprain pain should be low. Hepple stage V = subchondral cyst formation. Berndt and Harty stops at stage IV (displaced fragment).
• •Small lesions (under approximately 100-150 mm sq): bone marrow stimulation. Larger or revision lesions: OAT, allograft, or AMIC. MACI is NOT routinely commissioned by NHS England for talar OLTs in adults.