You may have a plantar fibroma. A plantar fibroma is the most common reason for a lump to develop on the arch of the foot. These are often small but can grow steadily to reach sizes of 2 inches or more. They may occur as a single lesion or they may present as multiple lesions, typically along the medial border of the plantar fascia. They are benign and are composed of dense, fibrous tissue found in the ligaments.
Causes of a Painful Lump
Many patients with plantar fibromas do not have any symptoms and when they do, it is often only a vague discomfort from “walking on a lump”. These masses can be treated non-surgically with a custom orthotic. However, if they grow larger or are a persistent source of discomfort, they should be removed surgically. Patients with plantar fibromas will usually report that they “just noticed the mass one day”. Plantar fibromas are usually located on the inside of the arch of the foot. They usually feel smooth and rubbery. They are not usually tender to touch, although they may become irritated with prolonged walking.
Diagnosing a Lump
X-rays are often negative but an MRI will show a smooth, consistent mass. Plantar fibromas are typically treated non-operatively, until they cause discomfort to the patient on a regular basis.
Non-Operative Treatment Includes
- anti-inflammatory medications
- shoe modifications
- the use of a soft-accommodating or well molded custom-made shoe insert
- Injections of corticosteroids can shrink the plantar fibroma
Operative treatment is typically avoided due to both the high recurrence rate and the difficulty with obtaining clear margins. Operative treatment involves excising (cutting out) the mass. Recovery and return to unrestricted activity and shoe wear is in the 1-2 month range.