Normal function of the walk cycle begins at heel-strike to midfoot and ends at push-off with the big toe. There is a specific passage of force that a normal foot functions in. When the foot begins to deviate from this passage, break down occurs.
At the beginning of the walk cycle the foot contacts the ground on the outside (lateral) aspect of the heel. From this point, the passage of force then moves up the outside aspect of the foot. The weight is then distributed medially across the metatarsal heads and out through the large toe.
In a normally functioning foot, approximately 60% of the force that passes through the foot is directed through the head of the 1st metatarsal or the big toe. This is the point of contact in the gait cycle when the pressure of the foot on the ground is the greatest.
When the foot fails to function properly and excessive pronation occurs, the foot unlocks and the big toe joint is pulled to the outside by a connecting tendon called the Adductor Hallucis Tendon. As a result a bunion forms.
Symptoms of Bunions
Pain in the bunion area generally occurs while a person is bearing weight or wearing tight shoes. As one begins to walk, pain or burning may occur on the outside of the big toe joint and at times on the top of the joint. When pain intensifies in the bunion area, one often off-loads that area. As a result, pain occurs in the metatarsal area, on the top outside of the foot, ankle, knee, and hip.
Cause of Bunions
Bunions generally develop when an excess amount of pronation occurs in the foot. The cause of pronation can be the result of trauma, genetic formation, ridged big toe joint, ankle fixation, leg difference, knee deformities, surgeries that failed to get results, various systemic conditions, or due to tightness in the calf muscles. In a pronated position, the foot becomes unlocked and as our body weight propels over an unlocked foot during the walk cycle, the 1st metatarsal joint is pushed up and inward. As this motion of the 1st metatarsal occurs, the big toe is simultaneously pulled to the outside by a connecting tendon of the adductor hallucis muscle. Repeat occurrence of this motion over time will cause the big toe to remain in this position. Once this happens the foot widens and a bump becomes visible at the base of the big toe on the inside (medial).
Improper fitting of shoe wear is the second most common reason bunions develop. When the design of a shoe is too tapered for a foot, it places excess pressure on the big toe joint. If the shoe is sized too narrow and short, over time a bunion may develop.
Finally, in rare cases, bunions have developed due to the result of trauma or a systemic disease, such as Juvenile Rheumatoid Arthritis.
Treatment of Bunions
There are several methods for treating bunions:
- A properly built set of orthotics is the most important conservative method used in treating bunions. They are used to prevent further development or post-surgical reoccurrence of the bunion. The orthotic supports the foot in such a way that increases direct ground contact with the big toe. Placing the big toe in such a way slightly reduces the severity of the bunion. In a case where the bunion is mild and also flexible, support from the orthotic may move the metatarsal bone enough and remove all discomfort. Because most bunions develop from an excessive amount of pronation, a properly built orthotic will position the foot in a more supinated, locked position as the body weight passes over the foot at midstance. This prevents the ground's reactive force from pushing the 1st metatarsal up and inward.
- Properly fitted shoes are necessary to treat bunions. Precaution needs to be taken to make sure shoes are long enough and accommodate the width of each individual person's foot. Shoes need to also be as rounded as possible in the toe area.
- Anti-inflammatory medications can help reduce the inflammation caused by shoe-irritation.
- Surgery should be a last resort and reserved for those bunions that are severe. The decision to perform surgery is based on a number of circumstances and should not be taken lightly.
- The majority of people who have developed bunions and who also experience over-pronation will greatly benefit from a stretching program for the calf muscle. The stretching exercise at the end of this page has been recommended by the American Orthopaedic Foot & Ankle Society.
- Adding rockers to the bottom of the shoe(s) may provide additional reduction of the pain in the joint, after foot orthosis and stretching.