Can you give me a quick summary on what causes bunions? I had a mild one on the right foot for years. Now all of a sudden, one has popped out on the left foot. It is really weird.
In many ways, hallux valgus more commonly known as "bunions" remains a mystery. What causes it? Why does it seem to run in some families but not others? Is it caused by wearing pointy shoes? If it is caused by shoe wear, why doesn't everyone who wears those shoes develop bunions? These and other questions are investigated in a recent review of the problem.
Here's what we know so far. Studies have been done that show shoe wear is a factor. But it isn't the only factor because some people who don't wear shoes also develop hallux valgus or bunions. Anatomically speaking, we know there is a problem in the line up of the bones of the first toe.
It's this bony misalignment that causes a disruption in the way the muscles of the toes and foot work. Without the necessary muscle balance, the bones remain at an angle to one another causing the distinctive pattern that suggests bunions. And once the bone angle and muscle balance have been disrupted, then the surrounding ligaments and joint capsule get stretched out (called laxity).
And there's one more anatomic piece to this problem. Normally, there are two tiny round bones underneath the base of the big toe. These bones are called sesamoid bones. They may be small but their influence is huge. The sesamoids help create a pulley mechanism that allows for normal movement of the big toe as you walk. They help absorb ground forces with every step you take.
In hallux valgus (bunions), the altered bony alignment moves the bones of the first toe away from the sesamoids. There is a downward spiraling effect that ultimately leads to instability of the big toe and foot.
Many studies have been done on the problem of hallux valgus. There are reports on the role of each individual anatomical and biomechanical change that contributes to the problem. For example, if you are born with a short big toe or extra long second toe, there is an increased risk (but not guarantee) that bunions may develop over time.
There is a need for further studies to really answer the questions of what causes this problem and how does it come about. The ultimate goal is to prevent hallux valgus with a secondary goal of treating it effectively when it does develop. Understanding each piece of the puzzle is bringing us closer to answering your questions and guiding others with this same problem.
A. M. Perera, FRCS (Orth), et al. Current Concepts Review. The Pathogenesis of Hallux Valgus. In The Journal of Bone and Joint Surgery. September 7, 2011. Vol. 93-A. No. 17. Pp. 1650-1661.
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