Overview

Bunions are painful swellings that develop most often on the inner side of the foot near the base of the first toe (hallux). Less frequently, bunions occur at the base of the fifth toe (called a "tailor's bunion").

Bunions result from inflammation and thickening of the bursa (fluid-filled sac in the connective tissue) and cause abnormal bone formation and misalignment of the toe.

Bunions can be related to inflammation or to degenerative disease (e.g., osteoarthritis). They cause redness, tenderness, and pain, and alter the normal position of the first toe.

"Hallux abductovalgus" (HAV) is a term that refers to the hallux going away (abducting) from the midline of the body and twisting so the inside edge touches the ground and the outside edge turns upward. Essentially, this term describes the deviation of the toe toward the outside of the foot.

Bunions worsen over time and cause discomfort, difficulty walking, and skin problems such as corns and lesions. Sometimes, a small fluid-filled sac (bursa) near the joint becomes inflamed (called bursitis), causing additional swelling, redness, and pain.

Causes

Bunions are one of the most common foot problems. They often run in families, which suggests that the inherited shape of the foot may predispose people to them.

Pronated feet (flatfeet) are unstable and often cause bunions. Body weight is repeatedly transferred to the hallux while walking, and in flat feet, this transfer of weight allows certain muscles to become stronger than others. This overpowering of muscles causes the toe to bend and deform.

Bunions may be caused by tight, pointy-toed, or high-heeled shoes, and shoes that are too small. Women get bunions much more often than men. Improper shoes exacerbate the underlying cause of unstable flatfeet.

Progression

Typically, bunions begin as a bump or outward bend of the big toe that is only a cosmetic concern. However, the misaligned, outward-bending toe stretches the ligaments that connect the foot bones and pulls against the tendons, gradually drawing the toe farther out of line. Over time, the big toe continues to twist until it no longer lines up properly with its corresponding metatarsal and the end of the metatarsal may become enlarged.

Pressure from the first toe can result in deformity of the metatarsophalangeal joint in the second toe, pushing it toward the third toe. In some cases, the second toe may ride over or under the big toe. At this point, the range of motion in the big toe is decreased, which is a condition called hallux limitus.

The condition becomes painful at this stage. The bunion changes the shape of the foot and the biomechanics of walking become altered. Normally, the big toe can bend at least 65 degrees, enabling it to be the last part of the foot to leave the ground during walking. However, with hallux limitus, the big toe cannot function properly and the body weight is transferred to the bunion.

Painful bunions cause the patient to compensate by walking in an exaggerated toe-turned-out manner, so the painful hallux does not have to bend as far. Walking with the feet turned out steadily forces the hallux even farther out, worsening the condition. Without treatment, the deformity eventually becomes disabling.

Original article.