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Bunion

What Is It, Causes, Treatment, and More

Author: Corinne Tarantino, MPH

Editors: Alyssa Haag, Ian Mannarino, MD, MBA

Illustrator: Abbey Richard

Copyeditor: Joy Mapes

Modified: 28 Dec 2023


What is a bunion?

A bunion, or a hallux valgus, refers to a bulge at the metatarsophalangeal (MTP) joint of the big toe, also referred to as the base of the big toe. The MTP joint is the link between the metatarsal bone (i.e., the long bone of the toe) and the proximal, or first, phalange (i.e., the short bone of the toe). Bunions are one of the most common foot problems, especially among older adults and individuals who frequently wear tight shoes or high heels.

The foot is composed of several bones that form the ankle (i.e., tarsal bones) and the long bones that extend out to form the toes (i.e., metatarsal bones and phalanges). A bunion occurs when the first long bone of the foot, called the metatarsal bone, moves medially, or towards the middle of the body, while the shorter bones that form the toe, called the phalanges, move laterally, or towards the outside of the foot. Consequently, a bunion develops as the metatarsal of the big toe moves further inward over time.

What causes bunions?

Bunions may develop due to a variety of biological or environmental factors, including arthritis, biomechanical factors, neuromuscular disorders, genetic disorders, and trauma. 

Arthritic conditions, such as rheumatoid arthritis, typically cause inflammation of many joints in the body and may affect the MTP joint. Long-term inflammation can lead to deterioration of the bones that make up the MTP joint, allowing the bones to shift and form a bunion over time. 

Biomechanical formation of bunions generally occurs due to excessive pronation, or turning the foot inward. Excessive pronation may occur as a result of the shape of an individual’s foot, such as flat-footedness, or may also occur when wearing high heels or tight shoes. 

Neuromuscular diseases, or disorders that impair an individual's nerve and muscular function (e.g., cerebral palsy), can cause uncontrolled foot movements that may loosen the MTP joint, increasing the risk of bunion formation. 

Genetic disorders, which are passed down from parents to children, can affect the tissue that connects bones (i.e., ligaments) throughout the body, including the MTP joint ligament. These disorders, which include Ehlers-Danlos syndrome, Down syndrome, and Marfan syndrome, can subsequently lead to bunion development. 

Finally, trauma to the foot, specifically resulting in amputation of the second toe, can create space for the phalange of the big toe to move towards the remaining toes and create a bunion

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Are bunions genetic?

Bunions are not necessarily genetic; however, some of the causes of bunions can be inherited, or passed down from a person’s parents. For example, the shape of an individual's foot is typically passed down through families. Additionally, some inherited genetic disorders can increase the likelihood of bunion formation in an individual. Other disorders, like rheumatoid arthritis, can run in families and may also make an individual more prone to bunion development.  

What does a bunion look like?

A bunion typically presents as a red or swollen bulge at the base of the big toe. Over time, the phalanges of the big toe may gradually protrude further outward as the bunion becomes more severe.

What are the signs and symptoms of a bunion?

Signs and symptoms of a bunion vary depending on severity. Regardless, all bunions appear as a bulge at the base of the big toe. A dull, achy pain and redness and swelling at the site of the bunion are common initial symptoms. Because a bunion can increase the pressure put on the toes, a person may also experience numbness or tingling. Walking tends to worsen these symptoms, while resting often provides relief. The bursa, a fluid-filled sac that normally cushions the space around the MTP joint, may become inflamed due to increased pressure from the bunion. The resulting inflammation, known as adventitious bursitis, frequently causes a painful, burning sensation. 

How is a bunion diagnosed?

A bunion is usually diagnosed through physical examination. During the physical exam, a clinician will typically ask about the severity of the symptoms, inspect the foot, and observe the person’s gait, or the way they walk. Depending on the physical exam, an X-ray may be ordered to confirm diagnosis of a bunion and classify the severity (i.e., mild, moderate, or severe). A weight-bearing X-ray, which requires the individual to stand on the foot of interest while the image is taken, can highlight specificities of the bunion deformity, including lateral deviation of the phalange of the big toe and narrowing of the MTP joint. Occasionally, a biopsy may be performed to rule out other potential diagnoses, such as infection, gout, or inflammatory arthritis.

How is a bunion treated?

Initial treatment for a bunion typically consists of conservative measures, like wearing supportive, well-fitting shoes with a wider toe box (i.e., the section of the shoe that surrounds the toe) or using orthotic inserts, which are removable shoe insoles that provide increased foot support. Occasionally, nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be prescribed to reduce swelling. While these approaches may relieve pain and discomfort from a bunion, surgery is the only curative option. There are a variety of options for bunion surgery, including reshaping the toe or fusing a joint together. The surgical approach selected generally depends on the severity of symptoms, cause of the bunion, and anatomy of the individual’s foot.

What are the most important facts to know about bunions?

Bunions, characterized by a bulge of the joint at the base of the big toe, where the metatarsal and phalangeal bones meet, are among the most common foot problems. Bunions may develop due to a variety of causes, including medical conditions (e.g., rheumatoid arthritis) or lifestyle factors, like frequently wearing tight shoes. Although bunions are not genetic, some conditions that increase the risk of bunion formation can be passed down from parents to their children. Bunions typically appear as a red and swollen bulge, with associated dull and achy pain, at the base of the big toe. Bunions are often diagnosed through a physical exam, which may include an X-ray. Conservative treatments, such as wearing well-fitting shoes and taking anti-inflammatory medications, are aimed at minimizing symptoms. If symptoms persist or worsen, surgery may be required to resolve the bunion.

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Related links

Anatomy of the foot
Bursitis
Joints of the ankle and foot
Rheumatoid arthritis

Resources for research and reference

Dini M, Parks C. Bunion. In: Papadakis M, McPhee S, Rabow M, eds. Current Medical Diagnosis & Treatment 2021. McGraw-Hill; 2021.

Parks E. Practical Office Orthopedics. McGraw-Hill; 2018.

Shibuya N, La Fontaine J. Bunion Deformity. In: Usatine R, Smith M, Mayeaux EJ Jr, Chumley H, eds. The Color Atlas and Synopsis of Family Medicine. 3rd ed. McGraw-Hill; 2019.