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Lateral Foot Injury - Cuboid Syndrome

Cuboid syndrome is also known as subluxed cuboid, dropped cuboid, peroneal cuboid syndrome etc. Due to the inconsistent use of terminology associated with this injury, cuboid syndrome remains a poorly understood condition in both athletic and non-athletic populations. In this blog, we will go through what it is, its associated symptoms, the widely accepted mechanism of injury, and how to treat it.


What is it?


The cuboid is the only bone that articulates with both the tarsometatarsal joint (Lisfranc complex) and the midtarsal joint (Chopart’s joint). There are multiple ligaments and the long plantar ligament securing the cuboid in place. However, these ligaments are more taut medially than laterally, thus, the calcaneocuboid joint tends to move in a medially posterior axis. As the cuboid is the only bone linking the lateral / outside column of the foot, it is the keystone to the stability of the foot.


Cuboid syndrome is defined as a disruption or subluxation of the structural congruity of the calcaneocuboid joint. This further irritates surrounding joint capsules, ligaments, and particularly the peroneal longus tendon.


Primary

  • Acute pain (immediate) or gradual onset as a sequela to a inversion ankle injury

  • Pain localised to the cuboid

  • Tender upon palpation over extensor digitorum brevis muscle

  • Weak propulsion in gait

  • Positive test on Midtarsal Adduction and Supination Tests

Secondary

  • Pain may radiate to 4th metatarsal bone

  • May experience redness or swelling

  • May have sulcus sign if there is severe subluxation

  • May have reduced ankle range of motion

  • May have pain with resisted ankle plantarflexion and eversion

  • May have pain with active inversion of ankle


Contributing Factors - These are the elements that increase the likelihood of causing cuboid syndrome but not necessarily the direct cause of the mechanism of injury.

  • Improperly constructed orthoses

  • Faulty shoe construction

  • Running on uneven terrain

  • Inversion ankle injury

  • Pronated/flat foot structure


What causes cuboid syndrome?


The widely accepted mechanism of injury is through a series of repetitive jumps when your foot continually pronates abruptly. The onset of symptoms can be acute / sudden or overuse / gradual over the course of time. It is mainly through multiple microtraumas to the ligamentous structure during maneuvers requiring maximum flexibility. A good example of this is when a ballerina goes into a plie or athletes/ runners who run with flat or overpronated feet.


Mechanism of Injury (in depth)


To fully understand the mechanism of injury, we must first understand how the foot and ankle normally operate in walking.


Stance Phase:

  1. Heel strike against ground

  2. Subtalar joint (ankle) pronates within safe range to allow the foot to adapt to uneven surface, helping with shock absorption at ground contact


During pronation, your midtarsal joint is unlocked and allows a degree of controlled flexibility to soften the impact. However, every degree of subtalar pronation that occurs produces an exponential increase in midtarsal joint instability resulting in an unsafe range of overpronation. Thus, people who have overpronation or flat feet are more prone to injuries due to poor stability and unnecessary strain on the soft tissue and ligamentous structures.


Stance into Early Swing Phase:

  1. From mid-late stance, your subtalar joints re-supinates in preparation for propulsion

During supination, there is a reduction in midtarsal joint flexibility into further pronation or supination. The peroneal longus acts as a dynamic stabiliser during this phase to prevent excessive supination from the tibialis anterior and posterior muscle through the help of cuboid. The cuboid behaves similarly to a pulley system and provides a mechanical advantage for peroneal longus. With added stability in the midtarsal and subtalar zone, this allows the soleus muscles to contract for propulsion.


On the other hand, if your subtalar / ankle joint is pronating during the early propulsion phase, the soleus muscle relaxes while your peroneal longus lifts the lateral / outside border of the foot which becomes increasingly unstable and leading to disruption and stress over the cuboid.


💡Did you know?


Around 80% of people with overpronation create naturally unstable and hypermobile feet further increasing the mechanical advantage of peroneal longus. This can potentially sublux the pronated, unstable cuboid during the early swing phase as the hindfoot attempts to re-supinate into propulsion.


Other than flat feet, another factor that predisposes people to an increased risk of cuboid syndrome is reduced or poor joint congruency. If the articulating joint surface or interface is not optimal (this can be affected by previous trauma such as fracture, ankle sprain or degenerative conditions like osteoarthritis), the midtarsal joint’s locking mechanism will be affected and unable to prevent excessive pronation.


Surprisingly, lateral ankle sprains account for the majority of cases. As the ankle goes into extreme plantarflexion and inversion, the peroneal longus tendon places dorsal and lateral force on the forefoot creating a closed packed position. This forces the cuboid in an inferiormedial direction potentially tearing the interosseous ligaments. Another proposed theory is the reflex contraction of peroneal longus which causes the cuboid into inferior medial direction.


What can we do?


During acute phases, pain management and relief are important for week 1 to 2. Common methods usually involve:

  1. Cuboid mobilisation - provides some degree of analgesic effect

  2. Low-dye arch taping - if the person needs to be active during the acute phase)

After pain is under control, the main focus will be addressing the underlying cause and other contributing factors. Thus, this part of the treatment may vary for each individual. Generally, most of the effort will be put towards exercise therapy which may involve:

  1. Stretching the peroneal longus

  2. Strengthening extrinsic and intrinsic muscles

  3. Calf Raises for gastrocnemius and soleus

  4. Proprioception

  5. Neuromuscular control i.e. if the person has signs of dynamic knee valgus due to poor hip control

Cuboid syndrome can often be missed whether it is in the athletic or non-athletic population. Due to the inconsistent use of terminology, we have yet to prove that cuboid syndrome involves disruption and subluxation of structural congruity of the calcaneocuboid joint. However, it is widely accepted that this injury is mainly caused by lateral ankle injury or movement requiring maximal flexibility. If you experience similar symptoms, remember that pain resolution should be followed up by an effort to address contributing factors to hopefully prevent recurrence.




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