10

FOOT AND ANKLE

Dan Cushman

DIFFERENCES BETWEEN THE SEXES IN THE FOOT AND ANKLE

Numerous intrinsic differences exist between men and women with regard to the foot and ankle. The shape, size, and architecture of the structures exhibit many distinctions between the sexes. The appearance of a photographed foot, for example, often can be described as masculine or feminine purely based on its appearance. Furthermore, social and cultural factors influence the feet, which also add to the dichotomy. These intrinsic and extrinsic differences play an important role in injuries. As will be demonstrated, women tend to have more disorders of the foot and ankle compared to men.

Anatomy of the Foot and Ankle

The foot is proportional to body size for both sexes. Numerous studies have demonstrated, however, that despite men’s larger body size, men’s feet are not simply larger versions of women’s feet (see Figure 10.1). The male foot, as expected due to the larger body size, is larger than the female foot in all foot measurements—the 20th percentile for foot length for men is 257 mm, which is the 80th percentile for women (1,2). When normalized to body height, however, men have a longer foot length and breadth than women. Women’s feet have been shown to be wider in the forefoot, with a shorter arch length and shorter metatarsal length than a man’s foot (2). They also have smaller calcaneus bones (3). Men have been shown to have a greater first toe height and outside of the ball of the foot length (2). For both sexes, longer feet tend to be narrower (4). It should be noted that some studies have found contradictory results, including no relevant differences between sexes (4); geographical and cultural variations may play a part. It has been theorized that women have undergone intersexual selection for smaller foot size (5). In other words, men may have chosen female partners with smaller feet.

Men also display larger ankle circumference, calf girth, and tibial size than women (2,6), again owing to the larger body size. When normalized to body height, however, other findings appear. Women have larger ankle circumference, calf height, and calf circumference (2). Men, in turn, have a larger ankle height, medial malleolus height, ankle girth, and bimalleolar breadth (2). They also demonstrate a thicker distal third of their tibias than women, with thicker cortices, when assessed by dual-energy x-ray absorptiometry (DXA) and histologic sectioning (6). Comparison of ankle cartilage between the sexes by MRI shows less cartilage (in volume, thickness, and joint surface area) in the distal tibia, proximal talus, distal talus, calcaneus, and total hind foot in men than women (7).

Differences in the muscles that control the foot and ankle also exist between the sexes. The tibialis anterior, lateral gastrocnemius, medial gastrocnemius, and soleus all demonstrated larger optimal pennation angles in men than women (8). This may account for differences in force production or risk for musculotendinous injury (9). Although men have demonstrated greater absolute strength than women in the foot, when normalized to body size, no large differences in strength between the sexes have been shown (10–12). Toe flexor muscle strength has been demonstrated to decrease more rapidly over time in women than men, however (10).

Biomechanics of the Foot and Ankle

Biomechanical studies of the foot and ankle with regard to difference between the sexes mainly focus on gait, both in walking and running. During the first years of walking, boys and girls already demonstrate differences in foot shape and dynamic loading parameters. Girls exhibit greater heel and forefoot dynamic loading, while boys demonstrate a broader midfoot, suggestive of a lower arch (13). As adults, however, women have greater contact area in the midfoot; men have higher peak pressure and peak force in the medial toe and forefoot as well as greater contact area in the central forefoot and heel areas (14). This has potential medical implications as high metatarsal pressure has been linked to an increased risk of foot/ankle disorders (15). Women also tend to walk slower due to a shorter stride length and also demonstrate a narrower step width (16).

FIGURE 10.1: The human foot.

For the foot, women have demonstrated a higher amount of first metatarsophalangeal (MTP) joint extension compared to men while running (17). Men demonstrate significantly greater peak rearfoot eversion (18), which has been theorized to contribute to increased strain on the iliotibial (IT) band. In runners, men had significantly decreased contact area in the medial and middle forefoot with an increased maximal force in the lateral forefoot, neither of which was seen in women (19). In jumping tasks, men and women load their feet differently during landings, with men displaying greater force-time integrals in the medial midfoot, lateral midfoot, medial forefoot, and lateral forefoot compared to women (20).

The ankle joint has been shown to have a greater range of motion (ROM) in all three axes for girls/women aged 9 to 20 (21). Interestingly, as they age, there is a greater decrease in the ankle joint ROM for women compared to men (21). While walking, this increase in stiffness for men is most prominent in the fourth subphase of the stance phase (22). However, women’s ankle joint flexor moments are significantly smaller than men’s throughout the stance phase (16). Women generate greater plantar flexion ROM with greater power during the pre-swing phase of gait (12,23). When examining ankle stability, professional female dancers exhibit longer time to stability compared to their male counterparts (24). In unanticipated cutting tasks, women had significantly larger peak eversion angle and significantly smaller peak inversion angle during stance phase (25).

The Effect of Shoes

Although men and women have distinct anthropometric characteristics, shoe-wear has been demonstrated to have an increasingly important part in injury and is the most extensively studied extrinsic factor causing injury to women (26). The two most commonly implicated shoe characteristics, often found in the same shoe, are an elevated heel and narrow toe box.

Men and women have different priorities when it comes to the health of their feet. In a study by Baumhauer, Mcintosh, and Rechtine (27), men and women were asked about the most important outcome factors with regard to their feet and ankles. These factors are listed in Table 10.1. Men chose “foot and ankle weakness” more commonly than women, while women chose “difficulty fitting into shoes” significantly more than men.

The high-heeled shoe (Figure 10.2) has been studied extensively in its relationship to injury (26,28). As heel height increases, plantar pressure shifts from the midfoot to the medial forefoot, with an increased vertical and anteroposterior ground-reaction force (29). These biomechanical factors lead to an increased rate of plantar loading, increased peak pressures beneath the metatarsal heads, and decreased time to maximal peak pressure (26). As the heel height increases, there is an associated increase in subjective discomfort. This is likely a significant part of the reason that women who wear shoes with high heels complain of foot pain and deformity compared to women who wear flats (26). In fact, there are reports that the frequency of foot problems in populations that have never worn shoes is low (30). Narrow toe-box shoes have also been correlated to rates of injury. Hallux valgus was not found until the development of narrow shoes during the late medieval period, when examining human remains (31).

TABLE 10.1: The Most Important Factors, in Order of Priority, for Each Sex in Terms of Outcomes for Their Feet and Ankles

Source: Adapted from Ref. (27). Baumhauer, JF, Mcintosh S, Rechtine G. Age and sex differences between patient and physician-derived outcome measures in the foot and ankle. Journal of Bone and Joint Surgery (American Volume). 2013;95(3):209–214.

FIGURE 10.2: High-heeled shoes, which are likely related to foot and ankle problems in women.

Hammer toes, neuromas, bunionettes, and hallux valgus have all been implicated from high-heeled, narrow toe-box shoes causing excessively high plantar pressures and toe crowding (26). Women bear the brunt of shoe-related injuries, which are felt to be related to high-heel shoes. Forefoot deformities are prevalent in 76% of women during their lifetime (32), with hallux valgus and hammertoes being the most common maladies. In the same study, it was reported that 88% of women wore shoes with a width smaller than their feet by an average of 1.3 to 2.5 cm. When examining groups of women with and without foot pain or deformity, the average difference between their foot and shoe width was only 0.6 cm in each group.

Of note, shoe-wear may play a larger effect on injuries in men in one subgroup—rock climbers. In one study of 144 rock climbers, male sex was independently related to the onset of foot disorders, as well as the use of high-type shoes (33). However, this may also be related to the higher degree of climbing difficulty with men.

Last, manufacturers of running shoes have long purported performance and injury-prevention benefits of their shoes. The high prevalence of running-related injuries has allowed for decades of advice about the “correct” type of shoe for runners. However, this still remains anecdotal and there remains scant evidence proving the effectiveness of running shoe type with injury prevention (34,35). Barefoot running and minimalist shoes, which are lightweight running shoes designed to promote more of a forefoot strike, have also been studied over the last few years as they had a surge in popularity. It is believed that more anterior foot strike and increased cadence afforded by these shoes may help limit injury rates, as evidenced by decreased ground-reaction force and impulse data (36), but data demonstrating decreased risk of injury are lacking. Some studies even suggest increased injury (37,38). It should be noted that minimalist shoes have been demonstrated to show more foot bone marrow edema (39) and increased plantar pressure (40) compared to subjects with conventional running footwear. Regardless of the footwear, male and female runners appear to have similar foot-strike patterns (41).

MUSCULOSKELETAL COMPLAINTS OF THE FOOT AND ANKLE

Ankle Sprains

Ankle sprains are one of the most common musculoskeletal complaints encountered in modern practice, with half occurring during athletic activity (53). Most commonly, the anterior talofibular ligament is affected, but the calcaneofibular, posterior talofibular, and anterior tibiofibular ligaments may also be affected. The sex-difference literature is mixed on this topic, primarily due to the differences among age groups and sprain types. Women have repeatedly demonstrated higher injury incidence rates than men (44), with rates for women and men at 13.6 and 6.94 sprains per 1,000 exposures, respectively (44). Interestingly, the prevalence between sexes is equivalent (10.6% women, 11.0% men) (44) and the risk of suffering a first-time ankle sprain was not significantly higher in one sex than the other (42). Rates of ankle sprains in high school athletes, as a whole, occur at a rate of approximately 3.1 ankle sprains per 10,000 athletic exposures (52).

Studies for ankle sprain incidence in younger patients are mixed (43,45–54). Men/boys between the ages of 15 to 24 have been shown to have higher rates of ankle sprains than their female counterparts, which is likely related to the high rate of injury with athletic activity and increased risk-taking behavior in that cohort (43,46,50,53). The highest incidence has been reported in young males, while it is more common in older women compared to older men (108). Girls have been shown to experience the injury 1.25 times as often as boys in sex-comparable sports (e.g., sports played by both sexes such as basketball or soccer) (52). Both boys and girls sustain ankle sprains more often in competition than practice, with risk ratios of 3.42 and 2.71, respectively (52). High school- and college-age women have demonstrated more Grade I injuries compared to males; however, there are similar rates of more severe ankle sprains (Grades II and III) between the sexes (47).

An examination of ankle injuries (predominated by ankle sprains, but not exclusive to that injury) in high school athletes by Nelson et al. (50) demonstrated the following:

After ankle sprain, men demonstrated an increased risk of residual symptoms compared to women (odds ratio [OR]: 4.78) (109). In this study, however, the male cohort included a larger percentage of athletes than the female cohort, which may have introduced bias.

In young athletes, 23% report chronic ankle instability, which was more commonly reported in high school athletes compared to collegiate. Women report chronic ankle instability significantly more than men (55). The higher incidence of ankle instability may be related to the increased time to stability (the time period that it takes for the ankle musculature to return to a baseline variation after jumping) exhibited in asymptomatic women than in men (24).

When examining medial ankle sprains, men outnumber women in incidence by a ratio of 3:1 (56). Medial ankle sprains tend to be higher-force injuries, in which men are more often involved. Due to the uncommon nature of medial ankle sprains, there is little in the literature looking at the sex differences.

In contrast, high ankle sprains and syndesmotic injuries have been studied most in military populations. Waterman et al. (56) found the incidence of syndesmotic injury to be 480 per 100,000 person-years with a nonsignificantly higher incidence in men (490) than in women (460). This value is felt to be much higher than the general population, however, as the cohort included those participating in rigorous physical activity on a daily basis. In a large cohort of emergency department visits in eight states, the incidence rate was lower than the previously mentioned study—2.15 per 100,000 person-years for men and 1.65 for women (57). The statistical comparison was not reported, but was likely significant given the large amount of subjects. In this study, the 18- to 34-year-old age group contained the highest rate of incidence. The incidence rate in the general population most likely lies somewhere between these two rates, and it is likely that men have a slightly increased risk of injury. The difference between sexes may be accounted for by anatomical differences (110), where men tend to have larger tibiofibular clear space with larger tibiofibular overlap (111). Additionally, as men tend to be more commonly involved in high-energy trauma, they are more at risk for unstable syndesmotic injuries (112).

Differences in incidence rates of ankle sprains between the sexes is likely due to many causes. A variety of hypotheses have been raised, including hormonal differences, neuromuscular control differences, anatomic variances, and ligamentous laxity differences (57,113).

Pes Planus

The foot is often viewed as three sets of arches—an anterior transverse arch, a lateral longitudinal arch, and a medial longitudinal arch, as seen in Figure 10.3. Pes planus, or flatfoot, is defined as a flattening of the medial arch (114). Ligamentous, tendinous, fascial, and muscular structures all play a role in the stabilization of the medial arch. Asymptomatic pes planus is generally considered to not be pathologic and is not commonly treated. Arch height has been shown to be a risk factor for lower extremity injury (115). Figure 10.4 demonstrates an x-ray of a patient with pes planus.

FIGURE 10.3: Arches of the human foot. (A,B) Anterior transverse arch. (B,C) Lateral longitudinal arch. (A–C) Medial longitudinal arch.

FIGURE 10.4: Lateral x-ray image of a 16-year-old girl with pes planus (flatfoot).

TABLE 10.2: Flatfoot Rates for Children

The prevalence rates for this condition have been studied in numerous populations, particularly in children, for which a greater array of management options exist, including plaster casting, splints, muscle training, orthoses, and specialty shoes. The prevalence rates of pes planus are shown in Table 10.2. A general trend is that boys have a higher prevalence rate than girls, but the rates are variable depending on diagnostic criteria and population studied. The arch height for boys has also been studied, and a significant increase occurs around the ages of 12 to 15 for boys and 10 to 15 for girls (116). The arch heights in boys age 7 to 15 tend to be lower than those in girls (116), which is not the case in adults (117). Boys also have a thicker midfoot fat pad, which may also play a part in the diagnosis of pes planus (118).

In adults, men have been shown to have flat feet significantly more often compared to women, with an odds ratio of 1.23 (65). Other associated factors include advanced age, greater body mass index (BMI), bunion, hammertoe, poor health, Asian and African American races, and white-collar occupation (63,64). One interesting factor for men is that those with pes planus were twice as likely to also have hallux valgus compared to men without pes planus (61). Men also tend to have a greater navicular drop in asymptomatic individuals, which may predispose them to the higher incidence (61).

In one prospective study of military cadets (60), 33 of 512 new cadets were identified as having pes planus, using relatively rigid inclusion criteria. Similar to the other adult pes planus studies, women had smaller feet and a lesser degree of pes planus, yet still sustained more injuries than men.

Hallux Valgus

Hallux valgus (Figure 10.5) is a deformity of the foot with first MTP joint subluxation and medial bony enlargement over time and is also commonly called a bunion. It has been shown to be more prevalent in older patients, African Americans, those with pes planus, and those with knee/hip osteoarthritis (61,69). Surgical correction for hallux valgus is a common orthopedic procedure (119). As previously mentioned, this malady appears to be related to the effect of shoe-wear—women who wore high-heeled shoes during the ages of 20 to 64 had an increased likelihood of hallux valgus (61).

FIGURE 10.5: Weight-bearing x-ray image of a 50-year-old man with hallux valgus.

Women show a greater incidence of hallux valgus than men in several studies (26,30,68–72). One author (71,72) reports treating 53 male feet over a 20-year period, compared to 812 female feet. The female predominance in hallux valgus is not only isolated to the older population—girls are also more likely to seek treatment than boys for the condition (120). The effect of BMI on hallux valgus appears to also differ between the sexes. In women, a higher BMI is inversely associated with the presence of hallux valgus, while in men, those with a BMI between 25.0 and 29.9 had an increased likelihood of hallux valgus compared to those with a normal BMI (61). The authors felt that the likely reason for this sex-based difference was that women with lower BMI may tend to wear more fashionable (narrow toe-box) shoes, but this was not proven. Additionally, as mentioned previously, there is a correlation between the presence of hallux valgus with the presence of pes planus seen only in men (61).

Plantar Fasciitis

Plantar fasciitis, which is more appropriately termed plantar fasciopathy, is a disorder of the plantar fascia, which extends from the plantar tubercle of the calcaneus to the metatarsal heads. It presents most commonly with pain in the medial portion of the plantar tubercle and affects approximately 2 million people in the United States alone (73). Common treatments include steroid injections, deep-tissue mobilization, foot orthotics, night splints, extra-corporeal shockwave therapy, and surgical release. One study demonstrated that men had lower levels of postoperative pain from plantar fascia release and a quicker return of function (121).

Differences in the prevalence of plantar fasciitis between the sexes are mixed, and the majority of the literature demonstrates similar rates between them (73,74). Women aged 40 to 60 have been described as having the highest incidence of the disorder (73). When looking at U.S. military recruits, women have demonstrated an increased rate of plantar fasciitis (1.96 times more than men). Women also tend to have more plantar heel spurs than men (3), which may suggest increased traction on the plantar fascia. The plantar fascia thickness at the point 1 cm distal to the insertion has been demonstrated to have different values between the sexes (122), which may play a part in these potential differences. Conversely, male runners have demonstrated a greater incidence compared to female runners (97). A major concern with plantar fasciitis is progression to plantar fascia rupture, which is associated with steroid injection and appears to happen equally between the sexes (123).

Morton’s Neuroma

Morton’s neuroma is a common forefoot complaint due to an inflamed plantar nerve without a known etiology. It affects the third web space of the forefoot most commonly and results in pain and numbness or tingling that radiates to the affected nerve distribution to the toes. Due to the debility caused by the pain, foot and ankle surgeons are commonly called on to perform neuroma excisions (78). One of the theories related to the etiology of the condition is narrow shoe-wear. It thus comes as no surprise that women are more commonly affected than men (75–78).

Morton’s neuroma accounted for approximately 50.2 out of 100,000 presentations to primary care providers in the year 2000 for men, and 87.5 out of 100,000 presentations for women (76). Middle-aged women appear to be the most commonly affected (75,77,78). In an Australian study, when patients required hospitalization for Morton’s neuroma, the condition was three times more likely to happen to a woman than a man. Most cases occurred in the 50- to 54-year-old age group in women (age 55 to 59 in men) (77).

Chronic Exertional Compartment Syndrome

Chronic exertional compartment syndrome (CECS) is a condition that most commonly affects the legs, with a reported incidence of up to 30% (124). It is characterized by reversible ischemia in an enclosed fibrosseous space leading to decreased perfusion and pain. Symptoms usually resolve with rest and without permanent damage, unless an athlete continues to exercise through the pain, which can lead to acute compartment syndrome. The increased pressure in the compartment can be measured, and this intramuscular pressure is used for diagnosis. This diagnostic method has been called into question (125) as it is common to have high pressures in asymptomatic individuals.

In a study by Baltopoulos et al. (79), 48 asymptomatic participants underwent compartment pressure testing before, during, and after exercise testing. The 48 participants consisted of 12 female high-level runners, 12 male high-level runners, 12 female recreational athletes, and 12 male recreational athletes. Compartment pressures increased during the test in all subjects, and decreased after exercise in all subjects, but not to the point of pre-exercise levels. The recreational athletes had lower compartment pressures than the high-level athletes. Men had higher compartment pressures than women in the pre-exercise and during-exercise time points, but no difference post-exercise.

Though the Baltopoulos et al. study may seem to suggest that men would be at a greater risk for compartment syndrome, this study was done on asymptomatic individuals. Some studies suggest that symptomatic CECS is similar between the sexes (81,82). A retrospective study by Davis et al. (80) looked at 153 subjects with CECS that were verified by elevated compartment pressures; women accounted for 60% of the patients. Women accounted for more of the CECS diagnoses in competitive soccer, track/cross-country, lacrosse, and field hockey. Men accounted for more of the CECS diagnoses in noncompetitive running. A study of Army servicepersons also found that female sex was significantly correlated with an elevated risk for CECS (83).

Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy (RSD), is a poorly understood condition that is characterized by a painful limb that is disproportionate to any inciting event and contains sensory, vasomotor, sudomotor, and/or motor signs and symptoms (126). It has two subtypes—type I, which does not relate to a dermatomal or peripheral nerve distribution; and type II (causalgia), which relates to a peripheral nerve lesion. CRPS is likely to have elements of psychological, sympathetic, inflammatory, and genetic factors all involved in its pathophysiology (84).

Women are affected more commonly than men with CRPS (84–87), though it should be noted that most studies encompass all areas of the body, not just the foot/ankle. Women of European descent have a 3.4- to 4-fold higher incidence rate than men, while two thirds of Japanese cases are women (84). However, Korean men seem to be slightly more affected than women (84). In children, more than 80% of those with CRPS are girls (84). Interestingly, overall outcome may not be related to sex (85). Female sex has also been identified as a risk factor for CRPS type I, particularly postmenopausal females with ankle fractures or dislocations (87).

Osteoarthritis

It is estimated that 10% of all people over the age of 65 have foot pain attributed to osteoarthritis (OA) (88). Despite its high prevalence, OA of the foot has received less attention than other joints. OA in the foot has been found to have the highest radiologic prevalence in the second cuneometatarsal joint (88), but the first MTP joint is the most common symptomatic joint (90). The prevalence of OA in the ankle is generally accepted to be lower, in the range of 5 to 100 persons per 10,000 (127,128) and most often attributed to a history of prior trauma (95,129). It can have a similar impact on quality of life as hip OA (130).

When comparing the radiographic rates of OA in the foot, women likely are more commonly affected. Though statistical significance was not reported, Van Saase et al. (90) reported larger female prevalence rates of radiologic grade 2+ OA in a large Dutch cohort in the tarsometatarsal joint and the MTP joints, for all ages over 40 (see Figure 10.6). Men had a greater prevalence only in the proximal interphalangeal (PIP) joints of the foot. For both sexes, the rates of OA increased with age, as would be expected. In a separate study, women were found to have a greater median number of foot joints affected by OA (diagnosed by x-ray) than men (88). Similarly, Roddy et al. examined the prevalence of symptomatic radiologic OA of the foot (89). This study demonstrated that the first MTP joint was most commonly affected. Women were more likely to have symptomatic OA than men, particularly in the older age groups. They were also more likely to have disabling symptomatic OA compared to men.

Hallux rigidus is a condition seen with degenerative osteoarthritis of the first MTP joint with corresponding reduced sagittal motion in the first ray. It affects approximately 2.5% of people aged 50 or greater (131). Women are more commonly affected than men (91–93). One potential contributing etiology may be evidenced in a study of ballet dancers, in which females with longer second toes had a higher incidence of hallux rigidus and correspondingly increased pain scores, while men had no ideal pattern of toe lengths (132). Hallux rigidus was found not to be associated with shoe-wear or elevated first ray (91), but there have been correlations with metatarsal head articular shape (i.e., flat versus chevron) and metatarsal adductus (92).

For the ankle, men and women appear to have similar prevalence rates of OA (Figure 10.7). Over a decade-long study, Valderrabano et al. (95) collected information on 390 patients with end-stage ankle OA, and the split between sexes was almost 50/50. A study examining total ankle replacements in Finland showed that 63% of surgeries were performed on women (94), but sex had no effect on outcome after total ankle replacement. As opposed to the foot, the majority of ankle OA comes from prior trauma. This appears to balance between the sexes, where men have a greater incidence of ankle ligament lesions while women have more malleolar fractures (95). Primary OA is relatively rare in the ankle and may be more common in men (95).

FIGURE 10.6: Prevalence of osteoarthritis in the first metatarsophalangeal joints of men and women.

Source: Adapted from Ref. (90). Van Saase JL, Van Romunde LK, Cats A, et al. Epidemiology of osteoarthritis: Zoetermeer survey. Comparison of radiological osteoarthritis in a Dutch population with that in 10 other populations. Annals of the Rheumatic Diseases, 1989;48(4):271–280.

FIGURE 10.7: Mortise view x-ray image of a 68-year-old man with post-traumatic osteoarthritis of the ankle.

Stress Fractures

Stress fractures are covered more in-depth in Chapter 12. However, specific to the lower leg, a few studies have shed some light on differences between the sexes. Common locations of stress fracture include the tibia, navicular, metatarsals, and fibula (133). A study by Changstrom et al. (134) tracked stress fractures in U.S. high school athletes and found that the foot and lower leg were the most common locations of stress fractures for all athletes. In sex-comparable sports (basketball, soccer, volleyball, track and field, and cross-country), girls had a greater number of stress fractures, though these were counts and not rates. The combined effect of sex and body location was not reported in the study. By comparison, out of a total of 387 stress fractures, there were 135 in the foot and 156 in the lower leg compared to only 12 in the ankle. A separate study (97) examined 2,002 patients with running-related injuries in British Columbia and did not show a difference in tibial stress fractures between the sexes, but it did show that lower BMI in female runners was associated with more tibial stress fractures, which has been demonstrated elsewhere (135). Metatarsal stress fractures have been demonstrated to be more common in male high school runners (135).

Other Musculoskeletal Disorders

•    For overall foot pain, a prospective study of older adults demonstrated a 4-to-1 female predominance (96). Interestingly, a subgroup analysis was performed demonstrating that impaired foot protective sensation was associated with falls in men (OR: 5.1).

•    Posterior tibialis tendon rupture has been shown to occur more commonly in middle-aged and obese women (136). No significant difference was seen in posterior tibialis injury in a running population between men and women (97).

•    In a study examining the results of surgical intervention on 34 patients with tarsal tunnel syndrome (137), 74% of the subjects were women, though it was not stated that these were consecutive patients, so it is heavily subject to selection bias.

•    In a running population, there was no difference between the sexes in the incidence of metatarsalgia (97).

•    Sesamoid prevalence in the feet was examined in a comprehensive systematic review and meta-analysis (138). Men and women had no difference in partition (lateral and/or medial sesamoid bones). There were more commonly fifth MTP joint sesamoid prevalence (1.47 times more common) seen in men, otherwise there were no other differences in sesamoid prevalence in the other joints between the sexes. Sesamoid pain was not studied.

•    A prospective study examining anterior ankle impingement without ankle arthritis (98) collected 42 male patients and just 4 female patients with a mean age of 29 years, though this is also subject to selection bias as they were all patients who elected to undergo surgery. Patient sex had no effect on postoperative outcome. A similar study of 55 consecutive patients with posterior ankle impingement who underwent endoscopic removal of bone fragments and/or scar tissue was performed (99), of which 30 were male and 25 were female (median age 29 years).

•    Lisfranc injury prevalence does not appear to be affected by a patient’s sex (101). Additionally, 2 years after isolated Lisfranc injury surgery, there was no association between sex and functional outcome (100). Densitometric differences have been identified between the sexes in the bones of the first tarsometatarsal joint (139).

•    Toe fractures are extremely common, with a prevalence of around 3% (103). In a Dutch study (103), over 30 months of consecutive phalangeal fractures of the foot were collected, of which incidence was split evenly between men and women. Prior studies have demonstrated male predominance, however (102). In the aforementioned Dutch study, women tended to have worse outcomes than men, though most respondents had excellent outcomes.

•    For metatarsal fractures treated conservatively, men have been shown to have better functional outcomes than women (105). Fifth metatarsal fractures of the Jones type occurred more frequently in men, while avulsion fractures occurred more frequently in women, and functional outcomes were equal between the sexes (104).

•    Ankle fractures that were treated surgically tend to have better functional improvement in men than women (140,141). Incidence of ankle fractures is roughly equal between the sexes (102,106), though talus fractures occur more commonly in men. Ankle fractures are more likely to occur in young men or older women (106). Men have a greater chance of having a Weber C ankle fracture than women (106).

•    Avascular necrosis of the sesamoid is uncommon, but is more commonly associated with women (107).

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