A bunion is formed by a growth at the large toe metatarsophalangeal (MTP) joint, resulting in the bones of that toe moving outward. It is unknown why bunions form. Symptoms include pain, redness, swelling, tenderness, and decreased range of motion.
What is a bunion?
A bunion is a growth at the large toe’s metatarsophalangeal (MTP) joint (see diagram below), where the metatarsal (inside the foot) meets up with the closest of the two phalanxes of the large toe, causing the large toe's bones to deviate laterally (outwards).
The medical term for a bunion is hallux valgus, where hallux is Latin for large toe, and valgus refers to phalanxes’ movement away from the midline. The term bunion is from old English for "bunny lump or swelling.”
Are there bunions that form on other toes?
A small bunion can form on the 5th toe, called a bunionette or tailor's bunion (see diagram below). It was given this name since tailors used to sit much as they would sew and develop these bunionettes from irritation of the 5th toe.
Who gets bunions?
It is estimated that ½ of all adults will develop a bunion, with more women than men. Even though women wear tight shoes more often than men, this is not felt to be related to the higher incidence of bunions. However, women’s weaker connective tissue may play a role.
Bunions are not purely a disease of adulthood; they have been found in 2% of children between 9-10 years of age. Bunions may also be formed by congenital abnormalities (birth defects) that make the foot more likely to have bunions.
Bunions are frequently associated with rheumatoid arthritis, an inflammatory arthritis where the body attacks its own tissues.
Why do bunions form?
It is not clearly known why bunions form. Tight shoes have been postulated as a cause of bunions but have not been proven; however, tight shoes with pointed toes cause bunion progression (make them worse). One study found people who wear loose-fitting shoes are just as likely to develop bunions.
Another study compared pathology (disease) in people who run barefoot to those who run SHOD (wearing sneakers or shoes) and found no significant difference. In other words, wearing shoes/sneakers did not make any difference in forming any foot disease, including bunions.
In a study done by Nix, they did a systematic review of the literature and could not find any issues leading to the formation of bunions.
In normal feet, the outer edge of the foot hits the ground first, and then the foot rolls inward, called pronation; however, in people with flat feet (pes planus), the foot "overpronates," meaning it rolls more, leading to the higher likelihood of bunion formation.
Gout is caused by excess uric acid levels in the bloodstream, which leads to uric acid moving into the joints and forming painful uric acid crystals. Gout can affect any joint but usually involves the 1st MTP joint: the same joint as bunions. However, the major difference is the pain and symptoms of gout come on suddenly, whereas the pain and symptoms of bunions appear gradually.
What are the symptoms of bunions?
The most common symptoms are pain, redness, swelling, tenderness, and decreased range of motion at the 1st (MTP) joint, discussed above.
The pain of bunions is usually recurrent, meaning it comes and goes, but it can also be constant. There can be numbness of the large toe. In addition, a person with a bunion may have difficulty putting on their shoes.
Due to friction and mechanical trauma, other foot symptoms associated with bunions are the formation of corns and callouses (see diagram below), in which there is an increase of skin tissue called hyperkeratosis (a thickening of the outer layer of the skin, made with the protein keratin).
Corns are usually on the top of the foot (called the dorsum), while calluses are generally on the underneath area of the foot (called the plantar surface). Corns are smaller and round, whereas callouses are larger and irregularly shaped. The corns are usually more tender to touch than calluses, but both can be painful when applying pressure.
How are bunions diagnosed?
The evaluating physician takes a history to ask the following:
- Was there a history of trauma?
- When the bunion appeared?
- When the pain started?
- Did the symptoms appear gradually or all of the sudden?
The physical examination evaluates the 2nd MTP joint for areas of swelling, tenderness, warmth, and lateral (outward) deviation of the large toe phalanxes. An infected joint can have the same tenderness and swelling but is usually hot to the touch, with more redness.
Laboratory tests include a white blood cell count (WBC) for infection and uric acid level for gout.
Imaging studies like plain x-rays evaluate the bones of the foot. For example, plain x-rays will show the growth of bone at the MTP joint and the lateral deviation of the large toe phalanxes. Arthritic conditions such as osteoarthritis and rheumatoid arthritis usually show bony changes, especially at the joints.
If a more detailed evaluation of the bones is required, a computed tomography (CT or CAT) scan allows the viewer to see three-dimensional cross-sectional views of the bones. It also allows viewing of the soft tissues, including tendons and ligaments.
A bunion’s medical terminology is hallux valgus, which is a growth at the 1st metatarsophalangeal (MTP) joint, causing the bones to deviate laterally, meaning outwards.
It is estimated that ½ of all adults will develop a bunion.
Even though tight shoes do not cause bunions, they make them worse.
Symptoms of bunions include pain, redness, swelling, tenderness, and limited range of motion. Corns and callouses can also develop.
Plain x-rays are essential to evaluate the bones.
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Hollander, Karsten, Christoph Heidt, Babette C. VAN DER Zwaard, Klaus-Michael Braumann, and Astrid Zech, ‘Long-Term Effects of Habitual Barefoot Running and Walking: A Systematic Review’, Medicine and Science in Sports and Exercise, 49.4 (2017), 752–62 <https://doi.org/10.1249/MSS.0000000000001141>
Nix, S. E., B. T. Vicenzino, N. J. Collins, and M. D. Smith, ‘Characteristics of Foot Structure and Footwear Associated with Hallux Valgus: A Systematic Review’, Osteoarthritis and Cartilage, 20.10 (2012), 1059–74 <https://doi.org/10.1016/j.joca.2012.06.007>
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