Bump on the side of my foot: possible causes

Finding a bump on the side of your foot can sometimes be alarming, especially if it causes discomfort or interferes with your daily activities. While most lumps are benign, some may be more concerning. This blog discusses the potential causes of lumps and how to diagnose them, enabling you to answer the question, ‘What is a lump on the side of my foot?’  

Common Causes of ‘What is a lump on the Side of My Foot’

Ganglion Cysts

Ganglion cysts are fluid-filled sacs that develop near joints or tendons. They are typically soft or firm and can change in size. Most cysts do not cause symptoms; however, some may grow in size and cause pain by pressing on surrounding structures, such as muscles, tendons, or nerves. 

Most cysts can be easily diagnosed with an ultrasound. However, an MRI scan may be needed if the ultrasound findings are atypical. 

Troublesome cysts can be treated with an ultrasound-guided aspiration. First, a local anaesthetic is used to numb the skin surrounding the cyst. Then, a needle is directed into the cyst to remove the thick fluid. Finally, a small dose of cortisone is injected into the residual scan to prevent the cyst from returning. Nevertheless, some cysts recur and may require re-excision.  

Bunionette

A tailor’s bunion, or bunionette, is a bony prominence on the outer side of the foot, near the base of the fifth toe. It is often caused by wearing tight or ill-fitting shoes that place pressure on the area.

Generally, we often try simple treatments first, such as wearing looser-fitting shoes and gel pads to protect the bunion from the side of the shoe. In more problematic cases, the bunionette can be excised. 

Bone Spurs

Bone spurs are bony growths that develop due to repetitive stress, arthritis, or abnormal biomechanics. These can occur on the side of the foot and may cause pain or irritation, especially when wearing shoes. A more common bony spur at the back of the heel is a Haglund’s deformity. It is often associated with Achilles tendonitis and bursitis.  

Generally, treatment for Haglund’s deformity includes a gel pad and a heel raise to reduce pressure on the back of the heel. Other treatments include anti-inflammatory medication and exercises to strengthen the calf muscles. In more complex cases, we may recommend injections or surgery.  

Lipomas

Lipomas are non-cancerous growths of fatty tissue. They are soft, movable, and painless, though they can become bothersome if pressed against a nerve or joint.

Usually, lipomas are diagnosed through a physical examination, although ultrasound is a good imaging modality for confirming the diagnosis. 

Generally, lipomas don’t need any treatment, although some can increase in size and cause pain by compressing surrounding tendons or joints. In rare cases, surgery may be necessary. 

Plantar Fibromas

Plantar fibromas are benign lumps that develop in the plantar fascia along the sole. While more commonly located on the bottom of the foot, they can occasionally appear near the inside or outside of the sole. Generally, they are small and don’t cause pain. However, some can increase in size, causing pain, particularly when wearing tight-fitting shoes. 

Fibromas have a distinctive appearance on ultrasound and can be easily diagnosed by an experienced doctor. 

In severe cases, we resort to simple treatments such as well-fitting shoes, orthotics, and exercises that stretch and strengthen the arch. Sometimes, we trial a cortisone injection under ultrasound to reduce swelling. Surgery should be avoided due to a high recurrence. 

Tarsal Coalition

In younger individuals, a tarsal coalition (an abnormal connection between two-foot bones) can present as a hard lump on the side of the foot. This condition often causes pain and stiffness caused by abnormal forces surrounding the abnormal bone connection. 

Generally, diagnosis is often made with an X-ray or MRI scan. 

We try simple treatments first, such as orthotics and rehab. In more severe or persistent cases, we recommend excision of the tarsal coalition. 

Accessory Navicular Syndrome

This condition occurs when an extra bone near the inside arch of the foot becomes prominent and painful. Generally, this extra bone is dormant and doesn’t cause problems. Sometimes, however, swelling in this extra bone occurs due to an ankle sprain, excessive physical activity, or poorly fitting shoes. 

We diagnose an accessory navicular with an X-ray, ultrasound or MRI scan. 

Generally, treatment for painful extra bone includes modifying activity and using orthotics. For more persistent cases, we use ultrasound-guided injections or surgical excision. 

Calluses

Excessive friction on the skin on the side of the foot causes calluses. The skin thickens, forming a lump that can be painful. 

Gel pads and orthotics can reduce friction between the foot and shoes. In troublesome cases, a podiatrist can help by trimming the skin to produce less friction.

Dyshidrotic eczema

Dyshidrotic eczema causes small, itchy bumps filled with liquid on the bottom of your foot. We don’t know the cause of this condition, but it may be related to allergies and/or stress. Often, corticosteroid creams and antihistamines are helpful. 

Soft Tissue Tumours

Though rare, malignant or benign soft tissue tumours can present as a lump on the side of the foot. Early diagnosis is essential for appropriate management. Some examples include PVNS or soft tissue sarcoma. Generally, an MRI scan is the more definitive investigation for suspected tumours. 

What is a Lump on the Side of My Foot: How to Diagnose

A Lump on the side of your foot requires a comprehensive assessment. Your doctor will ask about the onset of the lump, any associated symptoms (such as pain, redness, or swelling), and whether it has grown or changed. Activities, footwear choices, and past injuries are also important factors to consider.

Typically, a thorough physical examination is crucial for assessing the lump’s size, consistency, mobility, and tenderness. The lump’s location and characteristics often provide clues to its underlying cause.

Sometimes, the cause of the bump on the side of your foot is apparent and doesn’t need further investigation. In cases where your doctor is unsure, she may order other investigations, such as the following: 

• X-rays help identify bone abnormalities, such as bunionettes, spurs, accessory bones, or tarsal coalitions.

• Ultrasound: Helps visualise soft tissue structures, such as ganglion cysts or lipomas. It can also determine whether a lump is more concerning and requires further testing. 

• MRI: This procedure provides detailed images of bone and soft tissue, which are essential for evaluating complex or suspicious lumps. It is the investigation of choice for more concerning lumps that are painful or rapidly growing in size. Sometimes, a dye is used to get more information on the lump. 

• Biopsy. If there is suspicion of a tumour or other concerning pathology, a biopsy may be performed to confirm the diagnosis.

Final word from Sportdoctorlondon on What is a Lump on the Side of My Foot 

A bump on the side of your foot can stem from various causes, ranging from benign cysts to structural abnormalities. Accurate diagnosis of a lump on the side of the foot is key to effective management, so don’t hesitate to consult a sports doctor if you’re concerned. You should see a doctor if the bump on the side of your foot is rapidly growing or causing pain or discomfort, to ensure that nothing serious is happening. 

Related conditions to what is a lump on the side of my foot: 

• Ganglion Cysts 
• Haglund’s deformity and Achilles bursitis 
• Accessory Navicular Syndrome 
• Tarsal Coalition 
• PVNS (pigmented villodular synovitis) 

Click on the site of your lump on the side of your foot to identify possible causes