Cuboid syndrome is not common and is an often misdiagnosed foot injury. The cuboid is a pyramid-shaped bone on the outside of the foot and sits just in front of the heel bone. The peroneus longus muscle on the side of the leg, wraps around the cuboid bone, continuing to the bottom of the foot to insert onto the first metatarsal bone. This muscle’s job is the eversion of the foot, or when the bottom of the foot is rotated outwards. Cuboid syndrome occurs when the cuboid bone becomes partially dislocated or subluxed from the heel bone, causing pain on the outside, middle of the foot. The peroneus longus muscle exerts excessive force on the cuboid during movement, lifting it up and popping it out of position, causing subsequent pain.
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Symptoms
Cuboid syndrome causes pain on the outside, middle of the foot. The pain can occur after an ankle sprain or suddenly on its own. There may be diffuse swelling, redness and/or bruising around the area of the cuboid. Pain is aggravated by weight-bearing and side-to-side movements. Cuboid syndrome pain often leads to a limp when walking. A dimple on the top of the foot coupled with a fullness or protrusion on the bottom of the foot indicate a partial dislocation of the cuboid bone.
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Causes
Cuboid syndrome is poorly understood, but there are two proposed mechanisms of action (MOA) of this foot injury. It can occur at the same time or following an ankle sprain, when the ankle rolls over. When this happens, the peroneus longus muscle contracts as a reflex to counteract the force causing the ankle sprain. This reflex can result in subluxation of the cuboid bone. The other MOA is overuse and it is compounded by overpronation of the foot when walking. When the foot overpronates, the middle of the foot moves excessivel, causing the peroneus longus muscle to pull on the cuboid. This may result in cuboid syndrome.
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Treatment
The treatment goal for subluxation or partial dislocation of a joint is ensuring that the joint/bone goes back into its proper place. If cuboid syndrome has occurred, assessment and treatment from a lower limb clinician or primary care professional is important to avoid complications and long-term pain. A “cuboid whip” is a treatment technique known as manipulation and is carried out by “whipping” the cuboid back into place. If there is swelling, redness, bruising and pain, cold therapy will ease symptoms of cuboid syndrome. Custom foot orthotics will control overpronation of the foot and stabilize and reduce the overpull of muscles and strain on ligaments. Well-fitting and supportive footwear is key, as is safe stretching of the peroneus muscle to increase flexibility and suppleness and prevent overpulling on the cuboid.
