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Foot Bone or Joint Injury

Os Peroneum

Minute Read


Posted 5 months ago


Last updated: 21/03/2023


by James McCormack

What is Os Peroneum?

An Os Peroneum is an accessory bone found in the Peroneus Longus Tendon on the outer aspect of the midfoot of approximately 20-30% of the population. There is no known mechanical benefit of this extra bone, and in most instances, people go their whole life without knowing they have an Os Peroneum. However, if the Os Peroneum becomes overloaded or direct stress is placed on it, it can become inflamed and lead to Os Peroneum Syndrome.

Location of Os Peroneum Diagram

Os Peroneum Syndrome: Symptoms

The symptoms of Os Peroneum Syndrome include pain and swelling on the lateral (outer) aspect of the foot that can cause visible swelling and redness.

Walking barefoot, on uneven surfaces or wearing unsupportive footwear can aggravate the symptoms of Os Peroneum Syndrome.

The outer aspect of the foot around the Cuboid Bone is often tender to touch, while turning the foot outwards can exacerbate the symptoms of Os Peroneum Syndrome.

Os Peroneum syndrome is often misdiagnosed as other common conditions of the outer foot, such as Peroneal Tendonitis, 5th metatarsal fracture or a cuboid fracture.

Causes of Os Peroneum Syndrome

Os Peroneum Syndrome is caused by trauma or overload to the Os Peroneum or overuse of the Peroneus Longus Tendon.

Trauma can directly impact the Os Peroneum, resulting in a bone fracture of the bone while a severe ankle sprain can irritate the Os Peroneum.

Poorly supported footwear or repetitive impact can lead to overload and overuse of the Os Peroneum to cause Os Peroneum Syndrome, while we often see this in dancers and gymnasts.

Finally, a Peroneus Longus tear can result in a distal fracture of an Os Peroneum.

Os Peroneum Syndrome Diagnosis

A Physical Assessment by a Physical Therapist or a Sports Medicine Doctor can identify potential Os Peroneum Syndrome, but imaging is usually required to confirm the diagnosis.

An ultrasound scan can pick up an Os Peroneum, while an x-ray is also a cost-effective diagnostic tool.

An x-ray can identify the presence of a bi-partite Os Peroneum, a non-displaced or displaced fracture.

An MRI can rule out other conditions that can cause extreme foot pain.

Treatment for Os Peroneum Syndrome

In most cases of Os Peroneum Syndrome, ice, rest and anti-inflammatories can be sufficient to calm down the symptoms before increasing function levels.

In some cases, a walker boot is required to reduce inflammation, and a Physical Therapist can guide a patient through how to transition from a walker boot to an everyday shoe.

During this process, strengthening and mobility exercises are beneficial to address biomechanical issues that may be overloading the outer aspect of the foot. Gait analysis is beneficial to identify the need for stability shoes or insoles.

If treatment is unsuccessful, an ultrasound-guided steroid injection may be used to reduce inflammation in the area. While surgery is rare, it can involve removing the bone or repairing the Peroneus Longus Tendon.

Physiotherapy with James McCormack

This is not medical advice and you should consult your healthcare practitioners before removing a boot. and we recommend a consultation with a medical professional such as James McCormack before trying any of these exercises. James offers Online Physiotherapy Appointments.

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