My title of this blog may seem strange. Most people tend to lose their appetites for finger foods like sandwiches after looking and talking about feet, especially feet with bunions. I’m actually going to use the layered concept of a sandwich to explain why and how many bunions form.
What is a Bunion? A bunion is described as an enlargement of bone/tissue around the joint of the big toe. The medical term is “hallux abducto valgus deformity”, but commonly called a bunion. Bunions almost single handily keep podiatrist busy in this country. Yet, in third world countries where poor fitting shoes are not as common, bunions are not as common.
What Causes a Bunion? Although most people view bunions as a bone problem in the foot, in reality most bunions are truly caused by muscular imbalances in the foot. There are several layers of muscles in the foot, I like to use the analogy of sandwich when explaining the muscular foot layers and how imbalance between the layers can lead to a bunion. The first and third layers of foot muscles are the bread layers of the foot. The bread muscles (first and third layers) are called intrinsic muscles, meaning the muscles start and end in the foot and do not travel into the upper leg. These muscles hold the bones of the foot together and give it its shape (posture), just like the bread holds a sandwich together. The second layer of muscle are the long muscles of the foot, they actually start deep in the back of the leg and travel around the ankle and attach to the bottom of the foot. The long muscle of the second layer are very strong and help push our bodies trough locomotion, they are definitely the meat of the sandwich.
Problems occur when you try to make a sandwich without bread. Ponder this theoretical question, if you make a sandwich without bread, does it actually exist? (Enough with the Akins diet questions, I’m getting hungry) When the first and third layers of muscles that help stabilize the posture of the foot become week or inactive, the strong muscle of the second layer take over. There are two major long muscle that make up the second layer. One attaches to the tip of the big toe, and the other muscle’s tendon splits to attach to the bottom tips of the 4 small toes of the foot. When these long muscles become dominate in foot function, they cause hammer toes in the 4 smaller toes and a bunion in the big toe. (Hammer toes will be discussed in a future blog)
Bunions usually form in 4 stages. The first stage may not be very observable, but if you test the strength and function of the intrinsic muscles of the foot (bread muscles) they will be very weak and the balance of the foot will be stable. Over a long period of time if the dysfunctional muscle imbalances are not corrected in the first stage, an actual shifting of the great toe will occur due to the pull of the Flexor Hallucis Longus (meat layer muscle that connects to the tip of the big toe, pointed above by the blue arrow). Because of the orientation of the muscle and its attachment site, it will cause the big toe to move laterally (over to the smaller toes). In a normally functioning foot several of the intrinsic muscles provide adequate opposition to this pull of Flexor Hallucis Longus (ying and yang relationship). But, when the short intrinsic postural muscles are weak and turned off, the long muscle of the foot will over-compensate and structural changes happen. The final and fourth stage is when the prolonged pull gets so great that the actual metatarsal (forefoot bone that connects to the base of the big toe) becomes wedged in the opposite direction, and TA-DHA, you have bunion.
Why do Bunions Occur? I believe the muscular imbalances that cause bunions occur from either natural causes or un-natural causes. Natural causes of poor foot function are due to injuries or improper foot development during childhood. In both of these scenarios over-pronation of the foot is the driving factor for the resulting muscular imbalance that causes the bunion formation. Technically, I might be more correct in saying the lack of mid foot supination in the propulsion phase of gait is the problem (meaning: the main arch of the foot does not raise during push off). The most common injury to the foot is an ankle sprain, which often leads to a tight rear foot that leads to an overly mobile midfoot and pronation issues. Developmentally, if a child starts to walk, say at the age of 6-8 months, their brains are often not ready to coordinate the muscle actions of the foot, leading to learned over-pronation. (P.S. the normal age for walking is 12 months) Finally, the un-natural causes of muscular imbalances in the foot are improper shoe wear. I believe there is no coincidence that 90% of bunions are diagnosed in women in industrialized countries. Narrow toed high heeled shoes are the main culprit. These shoes are a mechanical nightmare for your feet! (Again, I will spend a full blog on the mechanics of wearing high heel shoes.)
How Can You Help? If you’re young and your balance is poor, or you are starting to see your big toe shifting, find a health care specialist who isn’t just going to tell you to wait a few years and then have surgery. Find an expert to give you a plan to restabilize your foot. If you sprain an ankle, don’t just walk it off, find someone with a strong background in sports medicine and get it checked out and properly rehabbed. Do not encourage your children or grandchildren to walk prematurely before they are ready. And if you are going to wear high heels, don’t walk in them!
Dr. Chris Feil