Survey results suggest that at least one-third of individuals at risk for foot pain or diabetic foot ulcers are wearing shoes that are at least one size too big or too small, which can further increase those risks. Proper shoe fit and foot health start with patient education.

By Stephanie Swensen, BSc, and Ran Schwarzkopf, MD, MSc      

The high prevalence of foot pain and poor foot health has increasing implications for the aging population. Recent data from the Framingham Foot Study demonstrated that approximately 25% of the population (19% of men, 29% of women) report generalized foot pain on most days.¹ Poor foot health appears to be most marked among elderly and diabetic patients, and a study by Menz et al found an 87% incidence of foot pain in older adults.²

Similarly, diabetic foot ulcers are among the most common and severe complications of diabetes, with an estimated lifetime risk of 15%.³ Among the numerous contributing factors, improperly fitting shoes play a significant role in the development and exacerbation of foot pain and injury. Thus, proper shoe size is a particularly important element of foot health and overall quality of life within these populations.

Ill-fitting shoes are a common mechanism for the pathogenesis of foot ulcerations and pain. Shoes that are too small produce constant localized pressure, most commonly on the medial and lateral surfaces of the foot. Too-large shoes can cause friction ulcers behind the heel as a result of the foot sliding within the shoe.^4,5 Additionally, foot-shoe size mismatches can disrupt the biomechan­ics of the foot and ankle, predisposing the wearer to pain and falls.^6,7

The high prevalence of individuals with unequal foot sizes further complicates proper shoe sizing and increases the risk of foot injury; prevention of this problem requires the purchase of different shoe sizes for each foot.⁸ One study by Kusumoto and Ashizawa showed that only 33% of their cohort had equal left and right shoe sizes.⁸ Therefore, in addition to footwear’s function as an environ­mental barrier, shoe selection should include consideration of the pressure, shear, and shock experienced by the foot. Matching the dimensions of each foot to its respective shoe will help minimize the negative effects of those forces.

Our extensive review of the literature reveals that improperly fitting shoes are often associated with the complications of foot pain and ulcerations, particularly within the elderly and diabetic patient populations. Additionally, our previous research demonstrates the prevalence of foot-shoe size mismatch within the population and the high proportion of adults who are unaware of their own shoe size.

Diabetes and foot-shoe size mismatches

One of the most pronounced pathophysiologic consequences of diabetes is peripheral neuropathy, which has been reported to occur to some degree in more than 50% of patients with diabetes older than 60 years.⁹ Severe peripheral neuropathy results in loss of protective sensation, increasing the risk of physical trauma.¹⁰ In an examination of factors contributing to diabetic foot ulcers, MacFarlane et al reported that skin rubbing from footwear was the most common precipitant of ulceration. In that study an estimated 20.6% of foot ulcers in patients with diabetes were due to the shearing force applied to the skin from ill-fitting shoes.¹¹

Patients with diabetes suffer from a multitude of lower extremity complications and are 10 to 30 times more likely to undergo lower leg amputation than patients without diabetes; 85% of nontraumatic amputations in patients with diabetes occur subsequent to foot ulceration.¹⁰ Properly fitting shoes are of utmost importance in the care of diabetic patients, as the consequences of shoe-related foot microtrauma are costly and because individuals with peripheral neuropathy may not be capable of noticing the discomfort of poorly fitting shoes. Practitioners should not only assess patients’ need for therapeutic shoes but also the correct size and fit of their patients’ shoes.

A recent study by Harrison et al⁷ examined correct shoe sizing in patients with diabetes. In this study two-thirds of the patients were wearing shoes that were incorrectly sized for their feet. Most notably, 45% of patients wore shoes of the incorrect width.  Additionally, 45% of patients reported previous foot problems, including ulcers, calluses, bunions, corns, or edema.

A previous study by Reddy et al⁵ showed that 37% of patients with diabetes were wearing too-tight shoes compared with 24% of general medical patients. Reddy further demonstrated that the wearing of tight shoes was associated with callosities in those with diabetic neuropathy. Interestingly, no increased incidence of callus was noted in those wearing tight shoes in the general medical group or in those with diabetes who did not have neuropathy.

Another study by Nixon et al¹² confirmed the discrepancies in foot and shoe size among patients with diabetes. They assessed 440 Veterans Affairs patients, 58.4% of whom had diabetes and 6.8% of whom had an active diabetic foot ulcer. Only 25.5% of these 440 individuals wore appropriately sized shoes, and those with diabetic foot ulcerations were 5.1 times more likely to wear poorly fitting shoes than those without a wound.

The findings from these studies demonstrate the necessity of adequate shoe sizing, particularly in the diabetic population most at risk for foot ulcerations and related complications. Repetitive foot measurements should also be encouraged, given the resultant progressive change in foot shape and size that occurs with the disease and with age. Concomitant daily foot checks will also lessen the risk of ulceration from footwear.

Risks in older nondiabetic patients

An examination of the literature reveals evidence that foot pain becomes increasingly problematic later in life in all adults, not just individuals with diabetes.  Burns et al showed that older nondiabetic patients have similar rates of foot disease as their peers with diabetes.¹³ In addition to diabetes, conditions including peripheral vascular disease, peripheral neuropathy, neuromuscular diseases, and inflammatory arthropathy, predispose older individuals to foot problems, as do poorly fitting shoes.

Foot pain is particularly detrimental in the older population as it can severely impact individuals’ functionality and independence. Characteristic age-dependent alterations in feet often complicate proper fitting of shoes in older populations. For example, studies have noted that with age, the width and height of the forefoot increase more than hindfoot width and height.^14,15

Improper and ill-fitting footwear also contributes significantly to functional limitation in older adults. Burns et al¹³ recently investigated the proportion of elderly people on a general rehabilitation ward wearing incorrectly sized shoes. Nearly three quarters (72%) of the 65 patients in the studied population were wearing ill-fitting shoes. However, only 6% had shoes that were too small while 65% had shoes that were too large. None of the six patients with diabetes were wearing correctly sized shoes. Incorrect shoe length was significantly associated with the presence of ulceration and pain.

Paiva de Castro et al similarly demonstrated improper shoe fit in a series of 399 older adults.¹⁴ Too-large shoes were identified in 48.5% of women and 69.2% of men; the feet of those wearing the wrong size had greater width, perimeter, and height than the feet of those wearing correctly sized shoes. Incorrect shoe size was significantly associated with ankle pain in women but not in men or in patients with diabetes.

In addition to foot pain, poorly fitting shoes have also been associated with an increased risk of falls in older individuals. Many studies have focused on the type of shoes implicated in accidental falls; however, very few have examined foot-shoe size mismatches. Barbieri et al conducted interviews with elderly patients who had fallen while hospitalized and found that poorly fitting shoes played a role in 51% of the incidents.¹⁶

Three main shoe features have been shown to affect postural stability: the cushioning properties of the midsole, the slip resistance of the outer sole, and the height of the heel. Combined with ill-fitting shoes, these factors might contribute to an increased rate of falls,¹⁷  and research has shown that foot problems are more prevalent in older patients with a history of multiple falls than in those who have not fallen or have fallen only once.²

Menz et al followed 176 residents of a retirement village for 12 months; 41% of the individuals reported falling during this period.¹⁸ Fallers had an increased incidence of decreased ankle flexibility, severe hallux valgus deformity, decreased toe plantar flexor strength, decreased plantar tactile sensitivity, and an increased rate of disabling foot pain. The authors concluded that interventions to address these factors, including proper shoe fitting and medical surveillance, can be part of a falls prevention strategy.¹⁸

Mickle et al made similar recommendations in their study, which assessed 312 individuals for hallux valgus, lesser toe deformity, and toe flexor strength.¹⁹ They demonstrated a 35% fall rate during the 12-month study, and concluded that reduced toe flexor strength and the presence of toe deformity increased the risk of falling among their study group of older adults. The authors noted that interventions designed to address these issues combined with appropriate and well-fitting footwear might lower the incidence of falls in this population.¹⁹

As with diabetic patients, practitioners should take special care to properly fit shoes to the older patients’ changing foot sizes to prevent the development of pain, falls, and limitations in mobility and function.

Our experience

Given the aforementioned importance of properly fitted shoes, particularly in at-risk populations, we sought to determine the proportion of adults who are unaware of their own shoe size in three very different New York City populations: a foot specialist private office practice, an academic diabetic foot and ankle clinic, and a charity care center serving the homeless. We also examined patient demographic data and history of diabetes and ulcers to determine potential associations with shoe sizes.²⁰ Of the 235 participants, 34.9% wore ill-fitting shoes at least one size too large or too small and 11.9% wore shoes with a discrepancy of at least 1.5 sizes. Additionally, more than 90% of patients did not know their shoe width.

In contrast to the findings of Paiva de Castro et al,¹⁴ which indicated that male gender was associated with foot and shoe size mismatch, our study results found a higher association between female gender and shoe size mismatch. We did not examine the association between foot and shoe size mismatch and foot pain as did Paiva de Castro et al did in their study, which showed a higher association among females between foot pain and shoe size mismatch.¹⁴

Like the findings of Kushumoto and Ashizawa,⁸ our study showed a statistically significant difference between the right and left foot size among patients with a foot-shoe size mismatch; in addition, 60% of our patients with a shoe-to-foot mismatch had a difference between their right and left shoe sizes. This finding further highlights the need to size the larger foot to prevent the detrimental effects of pressure that would result from sizing only the smaller foot.

Interestingly, a significant connection was found between prevalence of foot-shoe size mismatch and clinic location. The patients from the private practice office had a significantly lower rate of poorly fitting shoes than patients from both the academic diabetic foot and ankle clinic and the charity care center. However, the academic clinic and the private office had a similar payer mix, making difference in socioeconomic status an unlikely cause of the differing findings. We speculate that the lower rate of poorly fitting shoes among the patients from the private practice may be due to the lower rate of diabetes among this group. We recommend a high level of vigilance when monitoring foot-shoe size mismatch among diabetic patients.

Conclusion

Our findings confirm previously recognized observations that a large proportion of patients wear improperly sized shoes. Although differences were observed in various clinic settings, nearly all patients were unaware of their accurate shoe size, regardless of education level. Therefore, counseling on proper shoe fitting is warranted to prevent the numerous complications of foot-shoe size mismatch.

We recommend that practitioners integrate a routine manual foot measurement during the patient’s annual or biannual office visit. Foot measurement should include both foot length and width. Furthermore, as the results of our study have shown, a high rate of left-to-right side foot-shoe size mismatch exists, and we highly recom­mend measurement of both feet during the exam. Not only should the practitioner assess the patient’s foot size during the exam, he or she should also evaluate the proper fit of the patient’s shoes and the possible need for customized shoes. Such protocols will help eliminate foot problems that occur due to improper shoe fit.

Ran Schwarzkopf, MD, MSc, is an associate professor of orthopedic surgery at Brigham and Women’s Hospital and Harvard Medical School in Boston, MA. Stephanie Swensen, BSc, is attending New York University Medical School and is a research assistant at NYU Hospital for Joint Diseases in New York City.