Arch structure and injury patterns in runners

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Abstract

Objective. The purpose of this study was to determine if high-arched and low-arched runners exhibit different injury patterns.

Design. Non-randomized, two-group injury survey.

Background. Running-related injuries are thought to be related, in part, to lower extremity structure. High-arched and low-arched runners with their different bony architecture may exhibit very different lower extremity mechanics and, consequently, different injury patterns. It was hypothesized that high-arched runners will exhibit a greater incidence of lateral injuries, skeletal injuries and knee injuries while low-arched runners will show a greater incidence of medial injuries, soft tissue injuries and foot injuries.

Methods. Twenty high-arched and 20 low-arched runners were included in this study. Running-related injuries were recorded and divided into injury patterns of medial/lateral, bony/soft tissue and knee/foot and ankle for both high-arched and low-arched runners. A χ2 analysis was then employed in an attempt to associate injury patterns with arch structure.

Results. High-arched runners reported a greater incidence of ankle injuries, bony injuries and lateral injuries. Low-arched runners exhibited more knee injuries, soft tissue injuries and medial injuries.

Conclusions. Based on these results, high and low arch structure is associated with different injury patterns in runners.
Relevance

Different injury patterns are present in individuals with extreme high arches when compared to those with extremely low arches. These relationships may lead to improved treatment and intervention strategies for runners based on their predisposing foot structure.

Introduction

It is believed that many factors play a role in the development of injuries in the lower extremities of runners. Injuries are often reported to be due to overuse [1], [2]. In addition, lower extremity mechanics are thought to play a role [3], [4]. However, abnormal structure has also been implicated as a factor that increases risk for injury [5], [6], [7], [8], [9]. Although there are a number of studies regarding injuries in runners, specific relationships between structural deviations and injury patterns have not been well established.

Foot structure is commonly associated with lower extremity problems. Giladi et al. [10] demonstrated that high-arched (HA) or normal subjects were more likely to develop stress fractures than low-arched (LA) people. Similarly, Cowan et al. [11] reported that HA individuals had the greatest propensity toward injuries of the lower extremities when compared to runners with normal and LA structures. Additionally, HA individuals are reported to have an increased number of tibial and femoral stress fractures while LA subjects demonstrate a greater number of metatarsal injuries [12]. It was found that both HA and LA patients had greater incidences of knee injuries than patients with a normal arch structure [13]. Conversely, it has been reported that a high arch was protective against all injuries in runners [14]. The same study found no relationship between low arch and injuries. Finally, a recent prospective study of Navy Seals suggests the static characteristics of pes planus, pes cavus and rearfoot range of motion are risk factors for development of lower extremity overuse injuries in general [15]. Some investigators have found no relationship to the structure [3], [16].

Based on these studies, there does not appear to be a clear relationship between arch structure and injury pattern. Differences in the results of all of these studies may be related to the method of defining and categorizing arch structure. Some were based on visual observation [13], which has been shown to be unreliable [17]. Others used footprint measures [18], which may not characterize the bony architecture well. Finally, the criteria for placing subjects into HA and LA groups is often arbitrary resulting in HA and LA groups that include subjects with only mild deviations. For example, if arch height is normally distributed, then dividing the range of arch values into thirds (HA, normal, LA) may result in a significant number of normal individuals falling within the HA and LA categories.

Arch height may effect the distribution of injury in the lower extremity through its influence on the mechanical coupling between the subtalar joint and the knee. This coupling is related to the orientation of the subtalar joint axis. It has been reported that the subtalar joint axis is oriented 42° in the sagittal plane [19], which would be approximately equal motion of the subtalar joint in the frontal (inversion/eversion) and transverse (abduction/adduction) planes. Abduction and adduction at the subtalar joint translates to external and internal rotation, respectively, of the tibia. A low arch with a relatively low angle of inclination at the subtalar joint is thought to result in a higher component of eversion at the subtalar joint and a lower component of tibial internal rotation.

Nigg et al. [20] found that arch height did not influence the individual measures of eversion (EV) excursion or tibial internal rotation (TIR) excursion during the stance phase of running. However, he determined that 27% of the variance present in the ratio between these motions (EV/TIR) was explained by arch height. Additionally, Nawoczenski et al. [21] found that LA individuals had a higher EV/TIR ratio while HA individuals had greater relative internal rotation resulting in a lower EV/TIR ratio than LA runners. Both authors suggest that a higher EV/TIR with relatively higher EV present in LA individuals might place a greater strain on the foot and ankle. Conversely, a low EV/TIR ratio seen in HA individuals may place more stress on the knee secondary to a relative increase in transverse plane motion of the tibia.

It has been suggested that a pronated or planus foot loads the medial foot while a HA runner tends to load the lateral structures more [22]. This suggests that runners with planus or LA feet may develop more medial foot and lower extremity problems and those with cavus or HA feet, more lateral problems. These medial and lateral loads may also be transferred more proximally up the entire lower extremity. For example, genu valgum is often seen in individuals with pronated feet and may stress the medial structures of the knee.

LA individuals are typically thought to have mobile feet while HA individuals exhibit more rigid feet [22]. A HA rigid foot is likely to be less able to attenuate shock resulting in greater forces experienced by the foot and transferred proximally in the lower extremity. Conversely, LA runners with more mobile feet may require more control of the structures of the foot. Increased demand may be placed on the soft tissue structures such as ligaments and tendons necessary for providing this control and result in more injuries in these structures.

Although, many authors have speculated that abnormal structure results in associated injuries, few definitive correlations have been found. It has been difficult to establish a relationship between a single structural deviation and a specific injury as the etiology of injuries is multifactorial in nature. However, a single structural deviation, if large enough, may have a stronger correlation to an injury or group of injuries. Based on the previous literature, few studies utilized subjects with large structural deviations. Subjects with greater deviations in structure may be more limited in their compensatory strategies and more likely to present with specific patterns of injury.

Therefore, the purpose of this study was to determine if foot types could be associated with injury patterns. It was hypothesized that HA runners would exhibit a greater incidence of lateral injuries, skeletal injuries and knee injuries while LA runners would show a greater incidence of medial injuries, soft tissue injuries and foot injuries. This was an attempt to demonstrate different injury patterns were present in individuals with different foot structures.

Section snippets

Methods

A preliminary power analysis for the χ2-test using a 5% level of significance was conducted in order to determine the number of subjects required in each group. The study included 20 HA (10 females; 10 males) and 20 LA (12 females; 8 males) runners between the ages of 18 and 50 (mean 27.8 yrs; SD 8.1) with no neurological abnormality or history of foot surgery. Subjects were excluded if they were currently injured, ACL deficient or had a recent lower extremity surgery within the past 12 months.

Results

HA and LA subjects' characteristics are displayed in Table 1. There were no differences between subjects in height, weight or age. Injuries are reported in Table 2 and grouped by location. There were a total of 70 injuries in the HA group and 64 in the LA group. The χ2 analysis showed significant differences between the groups in injury patterns (Fig. 1). HA runners showed more lateral injuries and LA runners had more medial injuries (χ2=9.22,P=0.002). HA runners reported more bony injuries

Discussion

The distribution of injuries was consistent with previous studies of running injuries as summarized by van Mechelen [24]. The majority of the overall injuries in the current study were at the knee (23%), foot (22.2%), ankle (20%) and lower leg (19.4%). This places 84.6% of the total injuries at the knee and distally.

Injury laterality was found to differ significantly between the two groups with HA runners reporting more lateral injuries and LA runners showing more medial injuries. It appears

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