Subchondral lesions of the ankle joint

Anatomy: Cartilage and subchondral bone at the OSG

The upper ankle joint is primarily formed by the shinbone (tibia), fibula and the talus. The articular surfaces are covered with hyaline cartilage. Directly beneath this cartilage lies the so-called subchondral bone - a dense layer that absorbs loads, provides nutrients for the cartilage and stabilizes the joint surface.

• Articular cartilage: smooth, shock-absorbing surface
• Subchondral bone: load-bearing layer beneath the cartilage
• Talar dome: typical location for osteo/subchondral lesions

Disturbances in the subchondral bone often also influence cartilage health - and vice versa.

What are subchondral lesions of the ankle?

Subchondral lesions are structural changes in the bone directly beneath the articular cartilage. They can occur in isolation or be part of an osteochondral lesion (bone and cartilage). They are often in the context of sprain injuries and overuse.

• Bone marrow edema (BME): increased fluid in the bone as a sign of stress, microinjury or inflammation
• Subchondral microfractures/stress reactions: fine overload damage visible on imaging
• Subchondral cysts: fluid-filled cavities, often adjacent to cartilage defects
• Osteochondral lesion of the talus (OLT): combined cartilage/bone defect, possibly with loose fragments
• Rare: circumscribed bone necrosis (circulatory disorder) in the talus

The severity ranges from reversible stress reactions to substantial defects that can put long-term strain on the joint.

Typical symptoms

• Stress-related, deep pain in the ankle joint (often on the inside or outside over the dome of the talus)
• Start-up pain, often improving after short movement
• Tendency to swell, possibly joint effusion
• Feeling of insecurity or buckling when unstable
• Restrictions on movement, occasional blockage or snapping phenomena in osteochondral fragments
• Increase in symptoms when exercising on hard surfaces or downhill

Causes and risk factors

Subchondral lesions in the ankle joint are often the result of twisting trauma (supination/pronation), and more rarely of repeated overloading without a clear accident. Mechanical and biological factors also play a role.

• Trauma: Ligament injuries with compression/shear tension of the talar dome
• Chronic ligamentous instability with repeated microtraumas
• Malpositions (e.g. varus hindfoot) with local additional stress
• High training load, jumping sports, hard surfaces
• Overweight and inadequate footwear
• Accompanying cartilage damage
• Bone metabolism: vitamin D deficiency, osteopenia/osteoporosis
• Smoking and vascular risk factors (blood flow to the talus)

Diagnostics: from conversation to imaging

A careful diagnosis clarifies the cause, extent and stability of the lesion. In addition to the defect itself, the focus is also on accompanying factors such as instability or axis deviations.

It is important to differentiate from differential diagnoses such as pure synovitis, impingement syndromes, osteoarthritic changes or tendon pathologies.

Stages and classification

To classify osteochondral lesions of the talus, among other things: The stages according to Berndt-Harty (X-ray/CT) and MRI-based systems (e.g. Hepple) are used. Size, depth, limitation and stability are clinically relevant.

• Size: small defects < 1.5 cm² vs. larger lesions
• Containment: circumscribed (contained) vs. marginal (uncontained) defects
• Stability: attached vs. loosened/lifted fragment
• Accompanying findings: subchondral cysts, generalized cartilage damage

These criteria influence the treatment decision – conservative, arthroscopic debriding or bone/cartilage reconstruction.

Course and prognosis

Many subchondral stress reactions and bone marrow edema heal with consistent relief and appropriate rehabilitation. Persistent pain, larger defects or unstable fragments pose a risk of persistent discomfort and – in the long term – arthritic changes.

• Healing tendency: weeks to a few months for pure stress reactions
• Risk of relapse if instability or incorrect loading persists
• Larger defects/cysts: often have a longer course, sometimes require surgical repair
• The goal of every therapy: reduce pain, improve function, prevent progression

Conservative therapy: first relieve the pressure, then build it up in a targeted manner

Conservative measures come first. They aim to reduce pain, calm inflammation, heal bones and restore joint function.

• Relative relief: temporary reduction in walking distance; Depending on the findings, partial weight-bearing with forearm crutches, air walker/splint for 2–6 weeks
• Cooling, elevation, compression for swelling
• Short-term anti-inflammatory pain medications (if tolerated, not long-term)
• Physiotherapy: mobility, lymphatic drainage, pain-free maintenance of mobility, later strength and proprioception
• Stabilization and balance training to prevent recurrences
• Insoles/shoe advice: shock absorption, guidance (e.g. pronation control), if necessary temporary heel elevation
• Change of sport: alternative training with low impact load (cycling, swimming)
• Treatment of accompanying causes: e.g. B. Belt instability, axis deviation, weight management
• Optimize bone metabolism: check vitamin D status, adjust calcium intake; In the case of osteopenia, additional internal treatment may be required

Injections into the joint can relieve symptoms, but should be used as indicated and sparingly. Preparations containing cortisone are worth considering in individual cases in acute synovitis; Regenerative procedures such as PRP or bone marrow-based preparations are sometimes used in addition; the evidence at the OSG is heterogeneous. Individual information about the benefits and limitations is always a prerequisite.

Interventional and surgical options

Surgical measures are considered if relevant symptoms persist despite consistent conservative treatment for several weeks to months or if the size/location/stability of the defect suggests this. The aim is to reduce pain and restore stable joint surfaces - without guarantees, with realistic expectations.

• Arthroscopic debridement and microfracture: for smaller, contained defects; the induced bleeding promotes fibrocartilage formation
• Retrograde drilling (drilling): in subchondral cysts under an intact cartilage surface; If necessary, filling with bone substitute/bone chips
• Fragment refixation: for acute, well-preserved osteochondral fragments
• Osteochondral transplantation (OATS/mosaicplasty): for larger, circumscribed defects; Transfer of cylindrical bone-cartilage plugs
• Matrix-associated cartilage regeneration (e.g. AMIC) or cell-based procedures: selective, in specialized hands; Evidence from the ankle joint is variable in comparison
• Accompanying corrections: belt stabilization, correction of axis misalignments for load centering

Follow-up treatment depends on the procedure and size of the defect. Partial weight-bearing for 4-6 weeks, early functional physiotherapy and a gradual increase in load are common. The maturation of the repair tissue takes time.

Rehabilitation and return to sport

• Phase 1 (pain/swelling): relief, cooling, mobilization without pain provocation
• Phase 2 (function): mobility, coordination, proprioceptive training; everyday stress
• Phase 3 (strength/load): targeted muscle building, ABC running on soft ground
• Phase 4 (Return-to-Sport): sport-specific drills; Increase in load according to criteria (low pain, no swelling, full function)

Time reference values ​​(variable for each individual): everyday stress after conservative treatment often after 4-8 weeks, easy jogging after 8-12 weeks; After cartilage reconstructive procedures, it often takes 3-4 months to start running, changing direction/jumping sports after 5-6 months at the earliest.

Prevention and everyday tips

• Regular stabilization and balance training for the ankle joint
• Suitable footwear with good cushioning and guidance
• Progressive increase in load, breaks when pain begins
• Weight management to reduce joint load
• Treat ligament instabilities early, if necessary temporary tape/orthosis in sports
• Consider the surface: prefer soft, flat surfaces

When should you introduce yourself to the practice?

Seek medical advice if pain in the ankle joint persists for more than 2-3 weeks despite rest, if swelling/effusions keep recurring, if blockages occur or if you cannot return to everyday life without any symptoms after a twisting injury. Early, targeted diagnostics can have a positive influence on the course.

Your orthopedics in Hamburg-Winterhude

We provide you with comprehensive, evidence-based advice on subchondral lesions of the ankle joint - with a focus on conservative options and clear indications for interventions. Location: Dorotheenstraße 48, 22301 Hamburg. You can easily get appointments online via Doctolib or by email.