Medial Ankle Instability

The deltoid ligament is the primary medial stabiliser of the ankle. It has a superficial and a deep layer, which differ in anatomy and in what they restrain, and it works alongside the spring ligament.

The superficial layer. A fan-shaped sheet with a broad insertion, it arises from the anterior colliculus of the medial malleolus and runs as the tibionavicular, tibiocalcaneal and tibiospring ligaments to the navicular tuberosity, the sustentaculum tali and the spring ligament. Its primary function is restraint of hindfoot valgus; it is the primary restraint to eversion stress and a secondary restraint to external rotation. Its blood supply comes from branches of the medial tarsal artery; it is the layer more commonly injured in isolation, and it has the better healing potential.

The deep layer. Thick, cord-like anterior and posterior tibiotalar bands arise from the intercollicular groove and posterior colliculus and insert on the medial talus at its tubercle. This layer is the critical restraint to external rotation and lateral talar shift, and the deep posterior tibiotalar ligament is its strongest, most consistent band and the most critical for stability. A deep-layer injury indicates a severe force and is often associated with syndesmotic disruption.

The spring ligament. Its superomedial, medioplantar oblique and inferoplantar longitudinal bands support the talar head and maintain the medial longitudinal arch. It is intimately associated with the superficial deltoid through the tibiospring fibres, and the two act together as the tibiocalcaneonavicular complex. Spring ligament injury often accompanies deltoid insufficiency; the combined injury leads to valgus hindfoot and flatfoot deformity, and in chronic cases both may require reconstruction.

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What the complex restrains. The deltoid is the principal restraint to lateral talar translation and external rotation of the talus within the mortise, and a major restraint to hindfoot valgus, resisting 40% of valgus stress. Both layers contribute to resisting valgus tilt of the talus in the mortise.

Position matters. Band engagement is position-dependent: the tibiospring band tightens in plantarflexion, whereas the tibiocalcaneal and deep posterior tibiotalar bands tighten in dorsiflexion.

The deltoid and the syndesmosis. Deltoid competence is essential for syndesmotic stability. An incompetent deltoid permits medial clear space widening and lateral talar shift even with an intact syndesmosis, which is why restoring medial stability can normalise the mortise.

Why isolated injury is rare. The deltoid is 2-3 times stronger than the ATFL, and because of that strength medial ankle instability accounts for only 3-5% of ankle sprains. Most deltoid injuries occur as part of a more complex pattern: with a syndesmotic injury (conventionally quoted at 40-60%), a pronation-external rotation fracture, or stage 4 PTTD.

Acute injury. Acute deltoid injuries typically result from high-energy trauma with forced valgus and external rotation. The presentation includes significant medial swelling, tenderness over the course of the deltoid, ecchymosis extending to the hindfoot (a clue to a significant medial-side injury) and a positive external rotation stress test; weight-bearing is often impossible because of pain and instability. MRI shows ligament discontinuity with surrounding oedema, and treatment starts by identifying and addressing the associated injuries, particularly syndesmotic disruption.

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Chronic insufficiency. Chronic deltoid insufficiency develops from an untreated acute injury, from repetitive microtrauma in athletes (gymnastics, soccer), or from progressive deformity in PTTD. It presents with medial ankle pain, subjective instability and valgus hindfoot alignment. MRI shows ligament thickening, scarring or complete attenuation, weight-bearing radiographs may show a widened medial clear space, and treatment has to address the underlying biomechanical abnormality.

History. Establish the mechanism (valgus force, external rotation), previous ankle injury or instability, and the functional limitation. Pain with cutting or pivoting suggests rotational instability, and a history of flatfoot or PTTD matters in chronic cases.

Inspection. Medial swelling in the acute injury; valgus hindfoot deformity in the chronic one. Assess alignment (hindfoot valgus, arch height, forefoot abduction) and look for pes planus, which suggests concurrent PTTD or spring ligament insufficiency, for an antalgic gait, and for an inability to perform a single heel raise.

Palpation. Work systematically along the medial malleolus, the course of the deltoid (from the anterior colliculus inferiorly), the spring ligament (plantar-medial to the navicular) and the posterior tibial tendon. Where it is tender localises the injury and identifies the associated pathology that also needs treating.

Special tests.

• External rotation stress test - knee flexed 90 degrees, ankle in neutral, external rotation force applied to the foot. Pain and increased rotation compared with the contralateral side indicate deltoid injury.
• Valgus stress test - valgus force to the hindfoot with the ankle in neutral. Increased medial joint opening suggests deltoid insufficiency.
• Kleiger test - external rotation of the foot with the ankle dorsiflexed and the tibia stabilised. Pain at the medial ankle indicates deltoid injury; pain at the syndesmosis suggests combined pathology.
• Single heel raise and resisted inversion - for posterior tibial tendon function. Inability to rise, or no hindfoot inversion during the raise, indicates PTT dysfunction or severe deltoid insufficiency.

Radiographs. Weight-bearing AP, lateral and mortise views of the ankle, with AP and lateral views of the foot. They show any fracture of the medial malleolus, fibula or posterior malleolus; they give the key measurements (medial clear space, talonavicular coverage angle, lateral talar station); and in chronic cases they show valgus tilt, talar subluxation and arthritic change.

The medial clear space. Measured on the mortise view, it is normally less than 4mm and should equal the superior clear space; the deep posterior tibiotalar ligament maintains it by preventing lateral translation of the talus. Widening beyond 4mm, or asymmetry compared with the contralateral ankle, indicates deltoid insufficiency or syndesmotic injury, and weight-bearing films are essential for accurate assessment.

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Why stress views. Static non-weight-bearing films can look normal because the talus reduces at rest. A stress or weight-bearing view loads the medial side to unmask a widened medial clear space or talar tilt, and the diagnosis requires stress radiographs showing medial clear space widening (criteria below) or MRI demonstrating ligament discontinuity.

• Manual external-rotation stress view - a mortise radiograph taken while an external-rotation force is applied to the plantigrade foot with the tibia held.
• Gravity stress view - the patient lies with the injured leg dependent (lateral decubitus, ankle unsupported) and gravity supplies the external-rotation/eversion load, giving a mortise view without the examiner's hand in the field. It is about as reliable as the manual test for detecting deltoid incompetence in SER fractures and avoids irradiating the examiner.
• Weight-bearing views - for chronic instability, standing AP/mortise views (and weight-bearing CT) reproduce physiological load and reveal valgus talar tilt and peritalar subluxation better than a supine film.

Reading a stress view. Any one of these indicates deltoid incompetence:

• Medial clear space over 4 mm
• Side-to-side asymmetry over 1 mm against the contralateral ankle
• Medial clear space exceeding the superior clear space

It is the same test that decides whether a supination-external-rotation (SER) fibular fracture is "stable" (deltoid intact) or "unstable" (deltoid torn, needs fixation). The 4 mm cut-off and the side-to-side comparison are pragmatic rather than rigorously validated, and stress technique varies between centres, so interpret the number alongside the clinical stress examination rather than in isolation.

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MRI. Indicated for suspected deltoid injury, chronic instability and preoperative planning, using T1, T2 and STIR sequences in coronal, sagittal and axial planes. It shows the associated pathology (syndesmosis, spring ligament, posterior tibial tendon, osteochondral lesions, bone bruising), and in chronic cases ligament thickening, scarring or attenuation without a discrete tear. The deltoid is graded:

• Grade 1 - intact fibres with oedema
• Grade 2 - partial tear
• Grade 3 - complete disruption

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CT. For fracture characterisation, preoperative planning and assessment of arthritis. It gives superior bony detail and shows the subtalar joint, and 3D reconstruction helps with complex fracture patterns, at the cost of poor soft-tissue resolution and radiation exposure. Weight-bearing CT is an emerging technology for dynamic assessment of hindfoot alignment.

Medial ankle pain with a sense of "giving way" has several mimics. The key task is separating true medial instability (deltoid/spring incompetence with talar tilt or shift) from medial gutter pathology and tendon disorders that cause pain without instability.

Who, and how often it works. Non-operative management is first-line for isolated deltoid sprains without fracture or syndesmotic injury. The conventionally quoted success rate is 60-70%, leaving 30-40% for surgical consideration, but no study cited on this page measures it - the comparative series here all enrol operatively treated fractures.

Weeks 0-3: protection and immobilisation. A CAM boot or short leg cast, non-weight-bearing for grade 2-3 injuries; grade 1 injuries start protected weight-bearing after the first week. Ice, elevation and compression control oedema, with NSAIDs for pain if there are no contraindications.

Weeks 3-6: progressive weight-bearing. Weight-bearing as tolerated in the CAM boot. Gentle ankle range of motion begins, avoiding forced eversion, with isometric strengthening of tibialis posterior and gastrocnemius, continued until daily activities are pain-free.

Weeks 6-12: strengthening and return to activity. The boot gives way to a lace-up ankle brace or taping. Progressive resistance exercises focus on tibialis posterior and the invertors, with proprioceptive training (single leg balance, wobble board) and graded sport-specific work; return to high-level athletics may take 3-4 months.

When to operate. The absolute indications are:

• Acute deltoid disruption with syndesmotic instability requiring fixation
• Deltoid disruption with a medial clear space still widened (greater than 4mm) despite syndesmotic fixation
• Chronic symptomatic instability with functional limitation despite 4-6 months of therapy
• Stage 4 PTTD with deltoid insufficiency and progressive deformity

The relative indications are:

• High-demand athletes with persistent symptoms after 3 months of conservative care
• Deltoid injury with a medial malleolus fracture whose comminution prevents stable fixation
• MRI-confirmed complete deltoid rupture with poor tissue quality in the acute setting

Primary Repair - Acute InjuriesReconstruction - Chronic InstabilityCombined Procedures

Direct Deltoid Ligament Repair

Primary repair is performed when tissue quality is good and the deltoid injury is part of operative ankle fracture or syndesmotic fixation.

Set-up and incision. Supine, with a bump under the ipsilateral hip, a thigh tourniquet, and the foot over the end of the table or on a folded towel for access to the medial ankle. A curvilinear incision of 6-7cm is centred over the medial malleolus, running from just proximal to its tip distally along the deltoid; an existing medial malleolar fracture incision can be used instead.

Approach. Full-thickness skin flaps expose the medial malleolus, the deltoid and the tibialis posterior tendon. The saphenous vein and nerve lie anterior to the incision and are identified and protected; the nerve is at risk if the incision is extended anteriorly.

Assessing the deltoid. Before repairing anything:

• Identify the level of disruption, most commonly at the tibial origin or midsubstance
• Differentiate the superficial from the deep components
• Judge whether the tissue will hold a primary repair or needs augmentation
• Inspect for associated injuries: spring ligament, posterior tibial tendon, medial talar osteochondral lesion

Repair. Debride devitalised tissue conservatively, then:

1. Place suture anchors (3.0-3.5mm) at the anatomic deltoid origin on the medial malleolus: the anterior colliculus for the superficial layer, the intercollicular groove for the deep components
2. Use high-strength non-absorbable sutures (2-0 or 0)
3. Repair the deep layer first, as it is critical for rotational stability
4. Repair the superficial layer separately, with slight overlap
5. Tie down with the ankle in neutral dorsiflexion and 5 degrees of hindfoot inversion
6. Consider suture augmentation with an internal brace in high-demand athletes

Why that position. Neutral dorsiflexion with 5 degrees of inversion, not eversion or valgus, prevents overtightening that would cause stiffness while ensuring adequate tension for stability. The contralateral ankle is the guide to the right position.

The spring ligament. If it is injured (a palpable defect plantar-medial to the navicular, talar head uncoverage on the radiograph), address it at the same sitting with suture anchor repair or reconstruction.

Closure. The deep layer with absorbable suture and the skin with non-absorbable suture or staples, then a well-padded posterior splint with the ankle in neutral and the hindfoot in slight inversion.

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Deltoid Ligament Reconstruction Techniques

Chronic deltoid insufficiency with poor tissue quality requires reconstruction with autograft or allograft to restore medial ankle stability. The indications:

• Chronic symptomatic instability (greater than 6 months) that has failed conservative care
• MRI showing complete attenuation with no identifiable tissue to repair
• Revision after a failed primary repair
• Stage 4 PTTD reconstruction requiring deltoid stabilisation

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Graft choice. Hamstring autograft (semitendinosus or gracilis) is harvested from the ipsilateral knee. Allograft (tibialis anterior or posterior, gracilis or semitendinosus) avoids the autograft morbidity, and a tibialis posterior transfer is reserved for combined PTTD and deltoid reconstruction.

Tunnels. Identify the anatomic footprints of the superficial and deep deltoid on the medial malleolus, then drill with a 4.5-6.0mm bit:

• Anterior colliculus tunnel, exiting the posterior malleolus, for the superficial deltoid
• Intercollicular groove tunnel, exiting the posterior malleolus, for the deep deltoid
• Calcaneal tunnel at the sustentaculum tali for the superficial component
• Talar tunnel on the medial neck for the deep component, which requires a small talar neck exposure

Graft passage. Split the graft into two limbs, or use two separate grafts:

1. Pass the first limb through the anterior colliculus tunnel, out of the posterior malleolus, and on to the sustentaculum tali tunnel: the superficial deltoid
2. Pass the second limb through the intercollicular groove tunnel and on to the medial talar neck tunnel: the deep deltoid
3. Tension with the ankle in neutral dorsiflexion and 5 degrees of hindfoot inversion

Fixation. Interference screws (bioabsorbable or titanium) secure the grafts in the tunnels, or suture anchors at the insertion sites. Tension them appropriately without overtightening, and test range of motion and stability on the table.

Associated procedures. Concomitant pathology is addressed at the same setting: spring ligament reconstruction if it is insufficient (FHL augmentation technique), calcaneal osteotomy for fixed valgus deformity, and PTT reconstruction or FDL transfer for stage 4 PTTD.

Caution

Neurovascular structures at risk during medial ankle reconstruction include the saphenous nerve (anterior), the posterior tibial neurovascular bundle (posterior, on average 1.5cm from the medial malleolus), and the medial plantar nerve branch to FHB (distal dissection). Meticulous dissection and careful use of retractors are essential to prevent iatrogenic injury.

Management of Complex Medial Ankle Pathology

Deltoid insufficiency often requires several pathologies to be addressed together, particularly in chronic cases and in stage 4 PTTD.

Stage 4 PTTD with deltoid insufficiency. This is end-stage flatfoot with a valgus ankle and an incompetent deltoid, and the treatment turns on whether the ankle is arthritic and how far. Without ankle arthritis:

• Deltoid reconstruction (autograft or allograft)
• Spring ligament reconstruction (FHL augmentation)
• FDL transfer to the navicular, replacing the failed PTT
• Medialising calcaneal osteotomy to correct hindfoot valgus
• Cotton osteotomy if there is significant medial column instability
• Lateral column lengthening if forefoot abduction is severe

With ankle arthritis, the deltoid is not reconstructed if fusion is planned:

• Ankle (tibiotalar) arthrodesis if the disease is isolated to the ankle
• Tibiotalocalcaneal arthrodesis if the subtalar joint is also arthritic
• Pantalar fusion for panarticular disease

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Syndesmotic injury with deltoid disruption. Syndesmotic reduction and fixation is the priority, and the medial clear space afterwards decides the deltoid:

1. Through a lateral incision, fix the fibular fracture and reduce and fix the syndesmosis
2. Assess the medial clear space fluoroscopically
3. If it normalises (less than 4mm), the deltoid may be left to heal; if it remains widened (greater than 4mm), make a medial incision and repair the deltoid
4. Direct repair is preferred if tissue quality is adequate; consider internal brace augmentation in high-demand patients

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Outcomes. Combined procedures have success rates of 75-85%, with a longer recovery (4-6 months) and higher complication rates than isolated deltoid surgery.

Suture-tape (internal brace) augmentation. A strong, non-absorbable tape such as FiberTape, secured with anchors, spans the repaired or reconstructed deltoid as an independent load-sharing "check-rein", typically from a medial malleolar anchor to a talar (and/or calcaneal or sustentacular) anchor, recreating the deep and superficial vectors. It is not the primary repair. It protects the biological repair or graft while it heals, restrains external rotation and valgus, and is intended to permit earlier, safer rehabilitation, the same rationale as internal bracing of the lateral ligament.

When it is offered. In poor-quality tissue (chronic, diabetic, revision), in high-demand athletes, and to reinforce a repair that would otherwise be marginal. The evidence is largely biomechanical and short-term small series. The tape supplements rather than replaces anatomic repair, over-tensioning it risks stiffness or over-constraint, and so routine use is not established.

Early Complications

Wound healing problems occur in 5-8%, because the soft-tissue envelope over the medial malleolus is thin. Diabetes, smoking, peripheral vascular disease and steroid use add risk. Prevention rests on careful handling of the skin flaps, a closure without excessive tension and appropriate patient selection. Management ranges from local wound care to debridement and delayed closure for deeper dehiscence.

Saphenous nerve injury presents as numbness or dysaesthesia along the medial ankle and foot, in 10-15%. It is usually iatrogenic, from dissection or retractor placement, and most are neurapraxias that resolve within 3-6 months. Permanent injury occurs in less than 2% but can be debilitating; prevention requires identifying and protecting the nerve during the approach.

Posterior tibial neurovascular injury is rare (less than 1%) but catastrophic. The bundle is at risk during deep dissection for reconstruction or tunnel drilling, and injury presents with plantar numbness, weak toe flexion or vascular compromise. Prevention is through careful dissection and knowledge of the anatomy.

Late Complications

Stiffness and loss of motion affect 15-20% after deltoid reconstruction, more than after lateral ligament procedures. The loss is typically of dorsiflexion (on average 8-12 degrees) and subtalar motion, caused by the length of immobilisation, adhesions or overtightening at repair. Prevention includes early motion after 2 weeks of protection and avoiding excessive tension during reconstruction; treatment is aggressive physiotherapy and occasionally manipulation under anaesthesia.

Persistent instability follows reconstruction in 10-15%. The causes are technical failure (inadequate graft tension, tunnel malposition), unaddressed hindfoot valgus, progression of PTTD, or syndesmotic insufficiency, and it requires thorough re-evaluation with imaging to identify the failure mechanism. Management may require revision reconstruction, calcaneal osteotomy or salvage fusion.

Post-traumatic arthritis develops in 20-30% of patients whose deltoid injury accompanied an ankle fracture or syndesmotic disruption. Initial fracture displacement, the quality of reduction, articular cartilage damage and age over 50 years are the risk factors, and it presents with progressive pain and stiffness over 2-5 years. Treatment ranges from bracing, activity modification and injections to ankle arthroplasty or arthrodesis in severe cases.

Recovery takes longer than after lateral ligament reconstruction because the deltoid carries weight-bearing stability.

Weeks 0-2: protection. A posterior splint or CAM boot with strict non-weight-bearing. Toe wiggling and ankle pumps in plantarflexion and dorsiflexion only, with no eversion and no forced dorsiflexion. Sutures come out at 10-14 days, watching for infection, and pain is managed with multimodal analgesia, ice and elevation.

Weeks 2-6: early motion. Weight-bearing progresses from none to 50% by week 6, in a CAM boot with gradually more time out of it for exercises. Active ankle pumps and gentle inversion-eversion (no forced eversion) begin, with isometric tibialis posterior and gastrocnemius contractions; physiotherapy starts at week 3-4 for oedema control and supervised range of motion.

Weeks 6-12: strengthening. Full weight-bearing in the boot, then a lace-up or Arizona brace. Progressive theraband resistance focused on tibialis posterior, single leg balance and wobble board work, and pool walking, stationary bike and elliptical. Sedentary workers return at 8-10 weeks and manual labourers at 12-14 weeks.

Months 3-6: return to sport. The criteria are full strength, normal range of motion, negative stress tests and passed functional testing, and the progression runs from a walk-jog programme through straight-line running and cutting drills to sport-specific training. An external ankle brace is recommended for sport for 12 months, and a permanent brace may be needed for high-level athletics; 80-90% return to their pre-injury activity level.

• Routine vs selective deltoid repair in ankle fractures. Whether to repair the deltoid during fracture fixation remains contested. Comparative series (Woo et al; Whitlock et al) show repair restores a smaller medial clear space and reduces reoperation, but most authorities still favour a stability-driven, selective approach, restore the lateral column and syndesmosis, then repair only if the medial clear space stays widened. No adequately powered randomised trial exists.
• Deltoid repair vs trans-syndesmotic fixation. Some evidence suggests direct deltoid repair gives equivalent function with fewer hardware-removal reoperations than syndesmotic screws, but selection bias limits conclusions and suture-button fixation has changed the comparison.
• Significance of an isolated superficial deltoid tear. Cadaveric band-specific work (Gregersen et al) indicates the deep posterior tibiotalar band is often spared in SER injuries, so a superficial tear does not necessarily mean global deltoid incompetence. Dynamic stress assessment, not static MRI signal, should drive treatment.
• Reconstruction technique and graft choice. No consensus exists on autograft vs allograft, single- vs double-bundle reconstruction, or the role of suture-tape (internal brace) augmentation; recommendations are extrapolated from anatomic and small clinical series.
• Role of weight-bearing CT. Weight-bearing CT is increasingly used to quantify hindfoot valgus and subtle peritalar subluxation, but thresholds defining pathological medial instability are not yet standardised.
• Optimal medial clear space threshold. The widely quoted 4mm cut-off and side-to-side comparison are pragmatic rather than rigorously validated, and gravity/external-rotation stress views vary in technique between centres.
• The two most-repeated numbers on this page are conventional, not cited. "Conservative management succeeds in 60-70%" and "syndesmotic injury accompanies 40-60% of deltoid injuries" appear a dozen times each and are not traceable to any study cited here. None of the seven indexed papers on this page measures either quantity: the comparative series enrol operatively treated fractures, and the prevalence series (Crim) reports MRI findings in surgical candidates for lateral instability. Both figures are reasonable teaching approximations that reflect how these injuries behave, but quote them as convention and be ready to say so if pressed for a source.