Syndesmosis injury to the ankle joint

Anatomy and function of the syndesmosis

The syndesmosis is a strong ligament and membrane system that connects the tibia and fibula in the area of ​​the upper ankle joint in an elastic but stable manner. It consists of several parts: the anterior (AITFL) and posterior (PITFL) syndesmotic ligament, the interosseous ligament and the interosseous membrane, which extends further upwards.

• Task: Securing the fork (“malleolar fork”) around the talus and fine-tuning the ankle joint mechanics.
• Special feature: Low, physiologically necessary mobility between the tibia and fibula during stress.
• Neighborhood: Frequent accompanying injuries to the outer ligament, inner ligament (deltoid ligament) or bones (e.g. fibula).

If the syndesmosis is injured, the fine stability of the ankle fork can be disturbed. If left untreated, there is a risk of misalignment, cartilage overload and, in the medium term, post-traumatic osteoarthritis.

Causes and mechanism of injury

Syndesmosis injuries are typically caused by rotational and shearing forces, and more rarely by pure twisting trauma. Sports with rapid changes of direction, fixation of the foot on the ground or contact (soccer, rugby, American football, handball, skiing) are often affected.

• External rotation of the foot with the tibia/fibula fixed
• Forced dorsiflexion (strong advancement of the shin over the foot)
• Higher energy in falls or collisions

Concomitant bone injuries are possible: Weber C fibular fractures, bony avulsions on the posterior edge of the tibial or a Maisonneuve fracture (high fibular fracture).

Typical symptoms

The symptoms are often less localized than with a classic lateral ligament tear and are more localized above the ankle joint.

• Pain in the anterior and/or posterior fork of the ankle, often higher than lateral ligament pain near the ankle
• Increased pain with external rotation or dorsiflexion of the foot
• Swelling and tenderness along the syndesmosis
• Pain on exertion, possibly limping; In case of instability, a feeling of “folding away”
• Sometimes hematoma or pronounced soft tissue swelling

Examination and diagnosis

The diagnosis is based on clinical examination, functional and stability tests, and imaging procedures. The aim is to reliably detect or rule out relevant instability of the ankle joint.

• Anamnesis: Mechanism of the accident (external rotation, dorsiflexion, contact), localization of pain above the ankle joint
• Inspection/palpation: tenderness over AITFL/PITFL, possibly along the fibula
• Functional tests: squeeze test (compressing tibia/fibula proximally), external rotation test, dorsiflexion compression test
• Stability test comparing sides (careful, pain-adapted execution)

Imaging: X-ray, MRI and other procedures

Imaging is intended to detect bony injuries, assess the extent of fork instability and visualize ligament injuries.

• X-ray (AP/Mortise/Lateral): Assessment of the ankle joint fork (medial joint space, tibiofibular overlap/clear space), exclusion of fractures.
• Stress or strain images: can be helpful if instability is suspected, but are painful and not always clear.
• Whole leg/lower leg x-ray for suspected Maisonneuve fracture (high fibula).
• MRI: Gold standard for assessing syndesmotic ligaments and associated injuries (inner/outer ligament, osteochondral lesions).
• Ultrasound: dynamic assessment possible, especially as a supplement in experienced hands.
• CT (for fractures/operation planning): precise bony representation and assessment of the fork reduction.

Severity levels and classification

Syndesmosis injuries are classified depending on the proportion of ligaments affected and the stability of the ankle joint. It is important to differentiate between stable partial injuries and unstable ruptures with diastasis (deviation) of the fork.

• Grade I: Strain/partial tear without instability (AITFL stretched, interosseous portion intact).
• Grade II: partial rupture with questionable instability; often indicated by MRI and close monitoring.
• Grade III: Complete rupture with instability/diastasis; often combined with medial ligament/bone injuries.

In the case of simultaneous fractures (e.g. Weber C, posterior edge of the malleolus), therapy depends on the overall situation. Correct restoration of the fork is prognostically crucial.

Conservative treatment

Stable partial injuries (often grade I, selected grade II) can be treated conservatively in a structured manner. The aim is pain-adapted immobilization, protective mobilization and early functional rehabilitation.

• Initially: relief, cooling, elevation, compression to reduce swelling.
• Immobilization: Ankle joint orthosis or walker boot for approx. 2-4 weeks, if necessary with partial weight-bearing on forearm crutches.
• Pain and inflammation management: targeted and time-limited, individually tailored.
• Physiotherapy: gradual development of mobility (initially in a painless direction), muscle strength, proprioception.
• Sports break: Return to running and contact sports only after certain stability, usually after 6-10+ weeks.

Conservative courses should be closely monitored. Increasing pain, a new feeling of instability or a lack of progress are reasons for renewed diagnosis.

Surgical treatment

Surgery is considered if there is instability/diastasis, relevant concomitant injuries or conservative measures are not effective. The aim is the anatomical reduction of the ankle joint and a stable, functional fixation until biological healing.

• Syndesmosis stabilization with adjusting screw(s): temporary fixation of fibula to tibia; Metal removal if necessary after 8-12 weeks depending on load requirements.
• Suture button systems (e.g. “TightRope”): band-like, dynamic stabilization; early partial loading is often possible.
• Combined procedures: Treatment of accompanying fractures (fibula, posterior edge), if necessary suturing/refixation of AITFL/PITFL or deltoid ligament.
• Intraoperative image control (fluoroscopy, if necessary 3D/CT) to ensure the fork reduction.

The choice of procedure depends on the extent of the injury, accompanying findings, sporting/professional requirements and bone quality. There is no standardized procedure for all cases.

Follow-up treatment and rehabilitation

Structured follow-up treatment is crucial to safely regain stability, mobility and resilience. Times are guidelines and will be adjusted individually.

After screw fixation, metal removal can be considered, especially in cases of high sporting stress or discomfort caused by the screw. After suture button systems, removal is usually not necessary.

Course and prognosis

With timely diagnosis, correct stabilization (conservative or surgical) and consistent rehabilitation, good results are possible. Compared to a pure lateral ligament tear, returning to sport and work often takes longer.

• Return to everyday activities: often after 6-8 weeks, depending on activity and stability.
• Ability to play sports: often after 10-16+ weeks, later for complex injuries.
• Long-term risks with inadequate treatment: persistent instability, cartilage damage, post-traumatic osteoarthritis.

Possible complications

Even with careful treatment, complications can occur. Close follow-up care helps to identify problems early.

• Residual instability or misalignment of the fork (malreduction/diastasis)
• Delayed healing, persistent pain
• Screw-related issues (loosening/breakage) or irritation after implantation
• Heterotopic ossification/synostosis (ossification between tibia/fibula)
• Nerve/soft tissue irritation, rarely infections
• Late consequence: post-traumatic osteoarthritis

Prevention and tips

• Consistent rehabilitation after ankle injuries (strength, coordination, proprioception).
• Sport-specific warm-up and neuromuscular training.
• Appropriate footwear; For high-risk sports, taping/orthotics may be required during the re-entry phase.
• Early clarification if there is no improvement after a “sprain”.

When should you seek medical advice?

• Severe pain above the ankle after rotation or contact trauma
• Significant swelling/hematoma, inability to bear weight
• Feeling of instability or “slipping away”
• Persistent complaints > 1–2 weeks after the alleged “sprain”
• Numbness, cold or circulation problems in the foot

Our treatment concept – individual and evidence-based

We prioritize a careful clinical examination, targeted imaging and initially conservative measures, provided that the stability of the ankle joint is preserved. If there is proven instability or relevant accompanying injuries, we will discuss with you the options for surgical stabilization including a follow-up treatment plan. Decisions are made transparently and taking your sporting and professional requirements into account - without blanket promises.