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  • Writer's picturePaul Monaro

Ankle Injuries - Complications & Differential Diagnoses

Updated: Apr 16, 2020

With moderate to severe ankle sprains, isolated lateral ligament injury is rare. There is usually some degree of joint or other soft tissue trauma. Some of the most common examples are described below.

Medial Joint

When inversion injury stretches lateral tissues, it invariably compresses those medially. Chondral or osteochondral injury may result. The deltoid ligament is also vulnerable to a crush injury, particularly postero-medially, as most sprains involve plantarflexion and inversion. When the sprain involves an eversion mechanism (often with plantarflexion or pronation), the deltoid ligament may be torn, particularly the anterior (tibiotalar) component. As this is a more significant injury, it will often involve damage to other structures, such as the lateral ligament or inferior tibiofibular joint (see below). Such an injury may require a degree of immobilization, usually a CAM boot for 4 to 6 weeks.

Midfoot Sprain

This injury frequently involves the bifurcate ligament complex. If uncomplicated, these sprains generally heal quite quickly. Less common midfoot joint injuries should be considered. See below for a more detailed discussion regarding midfoot joint injuries.

Inferior Tibiofibular Joint Syndesmosis

Syndesmosis injuries are common, representing up to 20% of all ankle sprains. The usual mechanism is external rotation of the talus on the tibia/fibula, often in a degree of dorsiflexion. This is seen frequently in collision sports, particularly rugby league and NFL. A significant eversion injury, resulting in deltoid ligament rupture, can also affect the syndesmosis. Plain weight-bearing x-ray may demonstrate a diastasis – widening of the joint space, but is often equivocal. MRI will provide a clearer picture. Surgical stabilization may be required when there is moderate to severe injury. A CAM boot follows this, or less severe injury, then graduated rehabilitation.


The most common fractures associated with ankle sprains are base of 5th metatarsal, distal fibular, osteochondral (talar dome), anterior process of calcaneus (after bifurcate ligament injury), spiral fracture of the fibula (along with significant syndesmosis injury) and osteochondral injuries involving the navicular.

Subtalar joint sprain

This usually occurs in conjunction with lateral ligament injury, when the calcaneofibular ligament is ruptured. There may be a heightened feeling of instability, particularly on uneven surfaces. Treatment is usually conservative. Tendon Injury Inversion or eversion injuries can lead to partial tearing of peroneal or tibialis posterior tendons. These injuries are often associated with prolonged recovery.

Midfoot Joint Injuries - Differential Diagnosis:


1. Bifurcate ligament: The mechanism of injury will be a combination of plantar flexion, supination and adduction. A common complication of this injury is an avulsion of the anterior process of the calcaneus. This will be missed on a direct lateral view of the ankle, so an oblique XRay is recommended.

2. Dorsal calcaneocuboid ligament: this ligament is palpated slightly laterally & inferiorly to the bifurcate. The mechanism of injury is plantarflexion & adduction. The injury looks very much like a regular ankle sprain, however they tend to recover more quickly.

3. Dorsal talonavicular ligament: (top of foot) resists plantarflexion of the talonavicular joint, so will be injured with pure plantarflexion. There will often be an associated avulsion injury.

4. Lateral talocalcaneal ligament. This ligament is situated directly below the ATFL, & stabilises the subtalar joint. It is not present in everyone. If absent, an ATFL & calcaneo-fibular ligament tear can lead to an unstable subtalar joint.

Lisfranc Complex:The main ligament stabilising this complex is the intracapsular interosseous ligament, between the 1st cuneiform & 2nd metatarsal. There is no ligament between the 1st & 2nd metatarsals, so this ligament is the main stabiliser of the region. It also plays a key role in maintaining the transverse & longitudinal arches. The base of 2nd metatarsal is wedged between the 1st & 3rd cuneiforms. Similar to the ACL, the Lisfranc ligament has a poor scope for healing when torn, so moderate to severe tears require surgery. Failure to stabilise the region leads to early arthritis & severe dysfunction. Dr Lisfranc recognised how problematic these injuries were during the Napoleonic Wars - he simply amputated the patient’s foot at the level of the tarsometatarsal joints! These injuries are rare in the general population, approximately 1 in 50,000. However there is a 4% incidence in NFL, generally due to direct downward force of one player’s foot on another.

There are two main mechanisms:

- Direct trauma – plantar dislocation. As above – the 2nd metatarsal is ‘punched’ down, causing a

rupture of the inferior capsule.

- Indirect – an axial longitudinal force is placed through a plantarflexed & slightly rotated foot. This is the mechanism common to dance, with the foot in demi-pointe. The 2nd metatarsal is pushed anteriorly, rupturing the dorsal ligament.

There will be midfoot pain & tenderness to palpation. The patient will often have difficulty weightbearing, particularly on the toes. There may be diffuse dorsal swelling, and sometimes localised plantar ecchymosis.

Imaging: Textbooks recommend weight-bearing XRay, however this is often normal, as the patient maintains a supinated foot due to pain. A bone scan will show the injury, but is not specific. A CT will image the injury, particularly the fracture that is often present.

There are 3 levels or stages of injury:

Stage I: Dorsal capsular tear without elongation of the Lisfranc lig. These are generally stable. There will be a normal XRay & positive bone scan. Treatment is a NWB cast for 6 weeks. If still tender, a weight-bearing cast is put on for a further 4 weeks. On removal, orthotics are recommended with gradual return to sport.

Stage II: There is elongation or disruption of the Lisfranc ligament, with the plantar capsular structures remaining intact. A weight-bearing XRay, if positive, shows a diastasis (2-5mm, or 2mm greater than the opposite side) but no collapse of the longitudinal arch. The recommended treatment is open reduction & internal fixation. The options are a percutaneous screw or wire.

Stage III: There is disruption of the dorsal capsule, Lisfrac ligament & plantar capsule, with collapse of the longitudinal arch. There is usually an associated fracture. The ‘fleck sign’, on AP radiograph, represents a fracture of the dorsal 2nd metatarsal & is a subtle sign of severe pathology. The treatment is ORIF.

Cuboid Syndrome: This is associated with peroneal tendon injury or tendinopathy, often in a very pronated foot. A cuboid stress fracture sometimes occurs. Traction through the peroneus longus may cause subluxation of the cuboid, which is very painful. A manipulation or mobilisation to this joint often gives immediate relief.

Navicular stress fracture: There will be a poorly localised midfoot ache, worse c activity, and settling quickly with rest. The classic diagnosis is palpation of the tender ‘N’ spot (between the tendons of extensor hallicus longus & tibialis anterior). The diagnosis is often missed, with the average time from onset to diagnosis being 8 months. It is common in jumpers & sprinters who spend a lot of time up in a plantar flexed position, and occurs more commonly in females, at a ratio of 2.8:1. Bone scan is very sensitive for diagnosis, but MRI is the best option for determining the stage of the injury. Treatment involves strict NWB in a cast for 6 weeks. If still tender, this is reapplied for a further 2 weeks. Return to sport is then graded over the next 6 to 8 weeks. Up to 50% may be complicated by delayed or non-union, especially in smokers and other patients with risk factors for non-union. (Drinking a lot of soft-drink, particularly coke, can be a factor in bone de-mineralisation).


1. Brukner P & Khan K (2012). Clinical Sports Medicine, 4th ed. McGraw Hill.

2. Clayton, J (2017). Complications of an ankle sprain. Sports Physio, 2, 6-9.

3. 1. Matthew Stewart, (2011) - Course notes “The Essential Foot & Ankle’. Matthew is a foot/ankle specialist sports physiotherapist at Parramatta.

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