Historical Perspective

Herodotus of Halicarnassus records the first ankle sprain in sports in his historical writings from the time of the Greek and Persian empires when King Darius I of Persia twisted his ankle while hunting.⁴² Herodotus also documents the first use of exercise as a treatment in Western medicine. This is not surprising, since track and field events were an integral part of the early religious festivals held at Olympia, Delphi, Nemea, and Corinth, and the first date recorded on a Western calendar was a sports event, the Olympiad of 776 BC.^17,108,206 Paré was the first to point out that exercise of the limbs was essential to recovery after treatment of a fracture. For the physician treating an athlete, this approach reflects the essence of sports medicine.

Epidemiology

Sports participation has become a fundamental characteristic of American society. A survey of a few of the more popular sports reveals that about 17.7 million people play football, 14.5 million play soccer, 15.6 million play baseball, 28.9 million play basketball, and 13.6 million play softball.¹⁹⁴ Injuries to the lower extremities constitute the majority of injuries for most sports (Fig. 30-2). This is particularly true for the running, jumping, and kicking sports. Table 30-1 provides a look at injury rates calculated for the foot and ankle from studies done for various sports. As of 2006, yearly sports participation at the high school level had increased each year for the previous 17 years, reaching 53.5% in 2006.¹⁹⁵

All sports and recreational activities carry an inherent risk of injury. It is a natural consequence of pushing against the body’s physical limitations and being involved in challenging competition. Nevertheless, one of the goals of sports medicine is to reduce the health risks of athletic participation by recognizing and controlling the risk factors. From the vantage point of careful epidemiologic study, it is possible to identify and quantify risk along with the incidence and prevalence of injury for a given set of conditions.²²⁸

To analyze epidemiologic data properly, it is critical that the population being analyzed is assiduously defined. Many studies of athletic injuries that have engendered prejudicial thinking about the causes for injuries are flawed because of their methodology. Contemporary medicine favors evidence-based health care and outcomes-based research. Unfortunately, the literature in sports medicine, orthopaedics, and even medicine in general is overwhelmingly derived from reports and retrospective case series where the level of evidence is less than ideal. Many of these case series report an injury rate, but they often fail to accurately define the population at risk for injury. A good example is the prevalent idea that runners who pronate (or more precisely, overpronate) are at a greater risk for a running injury. The 1978 article by James et al¹²⁶ fostered this idea by noting that 58% of their 180 patients had a pronated foot configuration. This study does not take into consideration the total number of people in the running population from whom this select group was derived who also pronate but do not have an injury problem.

Another problem with many studies is failure to provide an accurate definition of the factor being analyzed. In sports injury studies this is often related to variations in the definition of what constitutes an injury from one study to the next. For example, it is difficult to compare ankle injury studies such as Rowe’s,²³⁸ where an injury is defined as anything that causes an athlete to require medical attention and lose time from participation, with studies with much stricter definitions and classifications, such as Torg and Quedenfeld’s.²⁷⁴ The comparison difficulties are magnified when the comparison extends across sports and across levels of participation, because an injury to a peewee football participant might have no relationship to what a professional rugby player considers an injury.

Finally, the homogeneity of the population being studied is important. This relates to such considerations as exposure to injury, age differences, gender differences, preexisting injury, and other confounding variables that might significantly influence injuries. For example, the third-string tackle who seldom plays in games has a much lower risk for a turf toe injury than the starting running back.

With these factors in mind, one can appreciate the differences between studies and the number of variables involved.⁵⁹ The risk factors for injury can be divided into intrinsic and extrinsic varieties. The athlete’s physical and personality traits constitute the intrinsic factors, and the training techniques, playing environment, and equipment are among the extrinsic risk factors. In this regard, several studies have demonstrated that weekly running mileage is the most critical factor in the risk of injury in the running population.^{39,163,171,222,288} When weekly mileage surpasses 64 km (40 miles), the risk of injury increases logarithmically. Other significant risk factors in runners include a history of injury in the recent past, having run for 3 years or less, and a recent major change in the training regimen or environment.

Etiologic Factors

Intrinsic and extrinsic factors have a potential role in the cause of injury to the athlete.⁵⁹ Analysis of these factors sometimes allows intervention that can reduce or eliminate the risk factor and thereby lower the risk of injury. This is the heart of preventive sports medicine. Examples of such intervention include rule changes in football to eliminate the “crack-back block,” “spearing,” and “head-to-head” contact, as well as improved generations of synthetic grass and underpadding brought about by research into the relationship between artificial turf and injury.^{158,213–215,253} Janda et al^127,129 found that 70% of softball injuries were related to stationary bases, and 56% of these injuries were to the foot and ankle. By substituting breakaway bases, they demonstrated a reduction in injuries from 1 in 14 games to 1 in 317 games (Fig. 30-3). Bahr and Bahr have similarly demonstrated the possibility of reducing ankle injuries in volleyball through an injury awareness program and training with a balance board.²⁰ These types of studies can clearly affect the health of athletes, and particularly their feet and ankles.

Although it is beyond the scope of this section to discuss all the potential risk factors involved in athletic injuries to the foot and ankle, a few of the more important ones are investigated. The factors most often mentioned in association with foot and ankle injuries in sports include anatomic or biomechanical abnormalities, lack of flexibility, poor muscle strength, muscle imbalance, shoes and orthoses, and the playing surface.

Biomechanical Abnormalities

Certain underlying anatomic conditions are often related to athletic injuries. Many runners and coaches place abnormal foot biomechanics in this category in the belief that the runner with excessive pronation has an innately higher risk for sustaining a running-related injury.⁵⁸ A prospective cohort study of collegiate cross-country runners found almost seven times increased risk for medial exercise-related leg pain in those with significant pronation.²⁸ Two other studies of runners found little correlation between anthropometric measurements (femoral neck anteversion, pelvic obliquity, knee and patella alignment, rearfoot valgus, pes cavus/planus) and risk for injury.^280,288 Only pelvic obliquity was a positive predictor of injury, and only in one study.

Dancers, like runners, are another population often studied for an association between biomechanical abnormalities and injury risk. Although dance medicine specialists often relate lower extremity injury to poor technique and misalignment,112,122,170 two independent studies failed to confirm such an association.^176,263

Studies of military recruits have provided much useful epidemiologic information because of the controlled nature of the population and their training regimen. A common injury among military trainees is the stress fracture. Although flat feet have been a disqualifying factor for military service in the past, some studies have shown that recruits with flat or pronated feet had no greater incidence of stress fracture than the remaining population.29,71,98 A study of the relationship between arch height and stress fractures in Israeli military recruits showed an increased incidence of metatarsal stress fractures in recruits with a low arch but fewer tibial and femoral stress fractures.²⁵² A study done on Navy SEAL trainees showed an increased risk of stress fractures of the lower extremity in recruits with either pes planus or pes cavus. It also showed that there was an increased risk of femoral stress fractures in trainees who had restricted hindfoot inversion and an increased risk of tarsal or metatarsal stress fractures in trainees with increased hindfoot inversion.¹³⁹

A study that attempted to correlate arch height with injury in runners found that transfer of foot eversion movement to internal leg rotation—a factor often related to knee pain—increased significantly with increasing arch height.²⁰³ However, arch height only contributed 27% to 34% of the variation in the transfer of movement between subjects. This indicates that other undelineated factors also influence kinematic coupling at the ankle–hindfoot joint complex, including the variation in plantar pressure pattern noted in runners with differing foot types.²⁵⁵ Theoretically, both the high-arched and the low-arched foot can cause impairment of subtalar and transverse tarsal joint function and thereby cause overuse injury.¹³⁹

All the answers are not yet available concerning this relationship between biomechanical differences and injury. Clinically, biomechanical alterations seem to be causally related to injury in some situations, but perhaps not to the degree that some sports gurus have suggested.

Flexibility

Pre-exercise or pre-participation stretching has long been thought to help prevent injury. A systematic review of the literature looking at neuromuscular warm-up strategies and injury prevention found a trend toward reduction in ankle sprains with practical neuromuscular warm up strategies which included stretching and proprioception training, including the use of a balance board. Results improved when exercise was maintained for more than 3 months and performed on a regular basis in each training section.¹¹⁵ Lack of flexibility has often been cited as the factor responsible for various sports-related complaints, although prior in-depth reviews of the literature have failed to show a correlation between stretching and the rate of injury. Thacker et al²⁷² and Krivickas and Feinberg¹⁴⁸ prospectively studied two components of flexibility—muscle tightness and ligamentous laxity—in college athletes. They found a significant association between lower extremity injury and both tight ligaments and overall muscle tightness scores in men but not women. Owing to their small numbers for individual sports, the data could not be analyzed for specific sports. Because a discussion of flexibility and stretching can evolve into an expansive section of its own, the present discussion is confined to relevant comments specific to the foot and ankle.

Lack of flexibility about the ankle and foot or limitation in motion of certain joints can be seen in association with certain disease processes or conditions, but the more common situation in the sports setting is single joint involvement, as seen in tarsal coalition. Athletes may have reached highly competitive levels of participation before the coalition limits them to the extent that they seek medical attention. They typically have a history of frequent ankle sprains, and the limitation in subtalar motion in these patients with talocalcaneal coalition may have been overlooked in the past.¹⁵¹

Restricted ankle motion in dorsiflexion is a factor in the anterior ankle pain seen in skiers and in runners who do hill work. This is often associated with anterior tibial and dorsal talar neck osteophytes at the ankle joint. Limited dorsiflexion of the ankle has been blamed for a multitude of other problems around the foot and ankle, including bunions,¹⁶⁹ turf toe,²³⁵ midfoot strain and plantar fasciitis,^141,153,262 ankle sprains,^287,268 Achilles tendinitis,⁵⁹ calf strains,^80,188 and excessive pronation (including all the problems that it can allegedly produce).^{42–44,60,139,167} All these conditions have been related to a tight Achilles tendon and its effect in limiting ankle dorsiflexion, but no studies have unequivocally documented this relationship.

Limited motion in the toes rarely receives much attention as an etiologic factor in injury or symptoms. However, a lack of flexibility is one of the critical components in the diagnosis of certain conditions such as hallux rigidus, which involves a characteristic loss of dorsiflexion in the first metatarsophalangeal (MTP) joint (Fig. 30-4).¹⁶⁸ In dancers with acquired hallux rigidus, restriction in great toe dorsiflexion to less than 90 to 100 degrees can produce compensatory positions that predispose the dancer to ankle inversion sprains and misalignment syndromes.^122,225 Limitation of motion in the other MTP joints is seen in patients with Freiberg’s infraction. When the interphalangeal (IP) joints of the toes are involved in loss of motion, a problem seldom exists unless an associated deformity is present, such as a hammer toe or mallet toe. These conditions in athletes can produce sufficient symptoms to require surgical treatment.

At the opposite end of the mobility spectrum, hypermobility is infrequently mentioned as the source of problems in the foot and ankle in athletes.⁹ Pathologic laxity is common to certain connective tissue disorders, including Ehlers-Danlos syndrome, Marfan syndrome, Larsen syndrome, Down syndrome, hyperlysinemia, homocystinuria, and osteogenesis imperfecta.^106,118,264 A hypermobility syndrome unassociated with known connective tissue disease has also been described as a potential source of musculoskeletal symptoms and signs, including ankle joint effusions.⁵⁹

In certain sports such as ballet and gymnastics, there is selectivity bias for the more flexible performer. Ballet dancers are particularly noted for the tremendous mobility in their feet and ankles. The same could be said for divers and gymnasts, who are awarded for having greater ability in achieving maximum plantar flexion so the foot assumes a pleasing line with the leg. Although this increased flexibility has obvious advantages, it may also have a negative side. Klemp et al144,145 have found an increased incidence of injury in ballet dancers who have greater mobility; others²⁹⁵ have failed to find such a relationship, however. While attempting to achieve the desired flexibility in ankle plantar flexion, the ballet student may develop posterior ankle pain from impingement with a large posterior talar process, calcaneal osteophyte, or os trigonum.²⁶⁰

A pathologic increase in joint laxity is termed instability.⁶⁰ Many studies have shown that a history of previous ankle injuries predisposes athletes to future ankle sprains.^79,295,305 Chronic instability of the ankle joint, a dynamic interrelationship between mechanical and functional factors, is a major factor in recurrent injuries to the ankle, whether it is due to a proprioceptive deficit, loss of ligamentous integrity, or some other condition.¹¹⁶ A study by Willems et al³⁰⁰ has shown that patients with chronic ankle instability have decreased proprioception at the extremes of inversion as well as decreased evertor strength when compared to normal counterparts. On the other hand, physiologic laxity has shown no similar trend.³³ Clinically the difficulty is in differentiating between these two conditions. This is clarified further in the ankle ligament section.

Strength

It is a commonly held belief that weak musculature predisposes a person to injury in sports. It is often stated that weak peroneal muscles are a factor in inversion sprains of the ankle, and one of the goals of rehabilitation after an ankle sprain is to strengthen these muscles. Fully activated strong ankle evertors exceed three-quarter-top shoes, taping, and orthoses in the protection they offer to the inverted ankle at foot strike.¹⁶ Several studies have shown that improving strength can reduce the risk for reinjury.* Most work in this area is related to strength in the thigh musculature about the knee. Similarly, muscle strength imbalances, which are viewed as creating a propensity for injury, have primarily been studied with reference to the quadriceps-to-hamstring ratio (ideally around 5 : 4 depending on the test method and test speed).^{12,146,198,263,303} Other studies have concluded that strength differences of more than 10% between the right and left legs increase the injury risk.^27,48 Ekstrand et al⁸¹ used this figure in their prospective study on the prevention of soccer injuries. They discovered a 75% reduction in injuries with a prophylactic program that included rehabilitation, to the point that 90% of muscle strength had been regained.

No similar ratios are found for the ankle and its proximal musculature to guide rehabilitation or expose a greater potential for injury to the leg, ankle, or foot. Silver et al²⁵⁰ performed the baseline work on strength of the leg muscles. They reported the ratio of plantar flexors to dorsiflexors as 6 : 1, or stated conversely, the dorsiflexors are normally only 17% of the plantar flexors in terms of strength. The peroneals have only 8.1% mean strength in comparison to the dorsiflexors at 9.4% and the plantar flexors at 54.5%. The peroneus brevis muscle has a mean strength of 2.6% and the peroneus longus a mean strength 5.5% in comparison to the strongest muscle, the soleus, at 29.9%.

Strength imbalance in the leg is a clear risk factor for injury to the ankle. Baumhauer et al²⁵ showed that athletes with a lower dorsiflexion-to-plantar flexion ratio had greater risk of injury. With a higher eversion-to-inversion ratio, the athletes had a higher incidence of inversion ankle sprains. This work was corroborated in a second isokinetic strength test study that showed invertor muscle strength deficiency was more important than evertor deficits in lateral ankle ligamentous injuries. A cohort study of professional soccer players in Greece showed an increased propensity for ankle sprains when athletes had preexisting functional strength asymmetries about the ankle.⁸⁹ Another prospective study failed to find a relationship between ankle strength and muscle reaction time with the risk of ankle injury.³³ Nevertheless, rehabilitation designed to restore the normal strength ratio through an isotonic and isokinetic strengthening program should reduce the risk of ankle injury.

The relationship between weakness and potential for injury in sports has been further corroborated by studies of soccer players. Backous et al¹⁸ performed a prospective study of boys attending a summer soccer camp, with the ankle being the most frequent site of injury. The highest incidence occurred in boys who were tall and had weak grip strength, which led the authors to conclude that skeletally mature but muscularly weak boys were at increased risk for injury compared with their peers.

Ekstrand and Gillquist found that soccer players who sustained a minor injury during the preceding 2-month period had a 20% increase in their risk of developing a more serious subsequent injury.78,79 Similarly, Bahr and Bahr¹⁹ noted a 42% increase in risk of reinjury in volleyball players who had suffered an ankle sprain within the preceding 6 months. This reinjury risk is attributed to inadequate rehabilitation and poor muscle strength and is supported by several studies.^{19,20,25,299,305}

With the weight of evidence supporting this association, this is the basis for working on strength as part of the rehabilitation process after injury or surgery. Furthermore, it is the precept on which college and professional athletic teams base their conditioning programs, including weight training.

Footwear and Orthoses

In the field of sports medicine, shoes have been blamed for athletic injuries caused by foot fixation on a playing surface resulting in increased rotational forces. This is the most often cited etiologic factor for noncontact injuries to the knee and ankle. Because of the obvious interdependency on the playing surface, these injuries are often attributed to the shoe/surface interface. Although this section deals with these two factors separately, the reader should keep in mind the relationship between them.

Rotational forces generated by the body at the shoe/surface interface are an important factor in sports injuries, but other factors are just as important. One of the most neglected but commonplace causes is improper fit of the athletic shoe. Just as this has been shown to be a prime cause of foot complaints in the general population, it is likewise a common source of relatively minor, although annoying, problems for athletes.59,60

When the athletic shoe is improperly fitted, the overly tight shoe causes pressure-related pain at the site of bunions and bunionettes, or it can cause metatarsalgia. When the athletic shoe is too loose, it allows the foot to slide, and blisters result. When the shoe is too short, the toes jam into the end. This can result in nail problems or the black toes of long-distance runners (Fig. 30-5). A more novel fitting-related problem occurs with tightly fitting ski boots, where excessive pressure at the ankle causes a neurapraxia of the posterior tibial nerve or the superficial peroneal nerve. Similarly, posterior tibial tendinitis or aggravation of an accessory navicular can occur from an ice-skating boot. Irritation of the Achilles tendon and production of a retrocalcaneal bursitis can occur from a variety of footwear, especially when there is a rigid heel counter. Careful fitting of the athlete can generally avoid or alleviate these types of problems rather than having to resort to surgical intervention (Fig. 30-6).

The shoe can be a source of problems in other ways as well, such as a lack of cushioning or lack of support. Load on the human body has been implicated as a specific etiologic factor in sports injuries.200–202,204 Because a significant component of this load is the vertical impact force or ground reaction force, cushioning, or shock absorption, by the shoe is an important property. The ability of shoes to prevent injury through improved cushioning properties has had mixed reviews in the studies of this subject. Greaney et al¹⁰⁷ showed a reduction in calcaneal stress fractures in military recruits by switching to tennis shoes. A study of South African military recruits reported a reduction in overuse injuries by incorporating a neoprene insole into the shoes used in training.²⁴⁶ A report on aerobic dance injuries included a mention of the beneficial effects of cushioned shoes in reducing injuries.²²⁹ However, a study of the U.S. Army Marching Band, whose members were switched to more cushioned shoes, showed no significant decrease in injuries.¹⁰⁹ Other studies have also shown no benefit from increased shock absorption in either shoes or insoles.^{90,135,185,186}

An interesting counterproposal to the idea that improved cushioning in the shoe is protective to the body is the Robbins and Hanna hypothesis.²³⁴ They have proposed that increased cushioning can actually be an etiologic factor in injury by dampening the body’s own sensory feedback mechanism coming from the plantar surface of the foot, thereby producing a “pseudo-neuropathic” condition.^232,233 This is a thought-provoking concept, and barefoot exercise or performance does appear to have some benefits. It has even spawned a new trend in running shoes—the “minimalist” running shoe (Fig. 30-7). Such shoes with little padding and arch support (with or without individual toe compartments) have become part of mainstream running. The traditional modern running shoe with increased cushioning and support allows more forceful heel strike and longer stride length while the minimalist shoe forces a shorter stride and better dispersion of forces across the entire foot. Improved dispersion of impact forces has been verified by biomechanical studies.²³¹ Future research will be needed to compare injury rates between cushioned and minimalist shoes.

Traction between the shoe and the surface can be separated into two categories: rotational (or torque) and linear (or shear). As traction increases, the forces on the knee and ankle increase as well, resulting in greater propensity for injury in these areas.²⁸⁹ One study proposed that two thirds of all non-contact soccer injuries were related to excessive shoe surface traction.⁸² Load on the body related to traction has been studied with reference to both rotational and linear forces.^{10,63,205,243,283} Several components contribute to traction in footwear design analysis. These include the outsole material, sole pattern, and the presence of cleats as well as their number, length, and pattern. Torg et al^274,275 studied football shoes and demonstrated precariously high torque when the shoes had ¾-inch-long cleats. Other shoe surface combinations were also considered potentially unsafe.^274–277 Softer outsole materials are also associated with increasing torque when used on artificial or clean hardwood court surfaces, but the presence of dust on the floor can alter this effect.²²⁷

Research has clearly documented the relationship between cleating of the athletic shoe and sports injuries.⁵⁹ In one study of high school football injuries, the number of ankle injuries was halved by changing from the traditional seven-cleated grass shoe to a soccer-style shoe.²³⁸ Further support for this came from Torg and Quedenfeld,²⁷⁴ who found a reduction in ankle injuries from 0.45 per team per game while using conventional cleats to 0.23 injuries in soccer-style shoes. Similar reductions have been reported in other studies evaluating other cleating patterns and surfaces.⁴¹ From the opposite standpoint, a lack of traction can potentially cause injury by increasing the frequency of slips and falls. Biener and Caluori³⁵ reported that slipping on wet tennis surfaces was a factor in 21% of injuries.

Clearly, problems can occur from either too much or too little traction. Athletes and coaches demand maximum traction for superior performance, but there comes a point where this can exceed the body’s ability to handle the load. A study of two shoes with treaded versus smooth sole design found increased traction with the treaded design, resulting in increased forces on the knee and ankle. Despite this, there was no difference in performance noted between the two shoes.²⁸⁹ An ongoing debate in the shoe equation as it relates to injury is high-top versus low-top shoes. Relatively few studies have scientifically investigated the value of different shoe heights in reducing ankle sprains. High-top shoes can be at least 50% stiffer than low-cut models and are affected by both the material and the geometry of the shoe.¹³³ This stiffness reduces the load carried by the collateral ligaments of the ankle. Conversely, when mobility necessitates use of a low-cut athletic shoe, the same mathematical model predicts the need for a low-stiffness shoe to allow maximum subtalar motion.¹³³ Theoretically the high-top shoe should stimulate the proprioceptive feedback mechanism, resulting in greater sensitivity of the peroneal muscles and improved stability for the ankle.¹⁰⁰

Garrick and Requa⁹⁶ found a reduced frequency of recurrent ankle sprains in college intramural basketball players who used prophylactic taping and high-top shoes. In another clinical study, Milgrom et al¹⁸⁷ found no evidence that high-top boots lowered the incidence of ankle injuries among Israeli military recruits when compared with three-quarter-top basketball shoes. A prospective randomized study of high-top versus low-top shoes reached a similar conclusion related to the prevention of ankle sprains.²⁴ Ottaviani et al²⁰⁷ have shown that basketball shoe height increases the maximum resistance to an inversion moment but does not affect the athlete’s ability to resist an eversion moment. According to one study, active ankle evertor muscles provide greater protection to inversion stress than three-quarter-top shoes, athletic taping, or orthoses.¹⁶

In recent years there has been extensive research into the biomechanics of ankle taping and bracing, which have shown differences in a variety of different biomechanical and neuromuscular measurements, including restriction of maximum ankle motion and improvements in peroneal muscle response during inversion movements.²⁹⁸ Ankle taping does improve proprioception, which is generally accepted to reduce the risk of injury to the ankle.⁶¹⁶ Nevertheless, there continues to be debate over the best method for preventing ankle sprains related to taping, bracing, and high-top shoewear.

Playing Surfaces

Load on the athlete as a factor in injury has led to a critical analysis of playing surfaces since 1980. This has primarily been stimulated by the introduction of artificial playing surfaces and particularly by the allegations that artificial grass causes increasing injury rates. Although substantial attention has been given to this subject in both the lay and the medical communities, there is still substantial debate over the degree and manner by which playing surface differences (particularly artificial turf vs. natural turf) increase risk of injury in sports.59,73,184,247,297 It does appear that third- and fourth-generation artificial turf have only minimal differences in injury rates compared to natural turf except perhaps for ankle injuries occurring more frequently on artificial turf.²⁹⁷

Although artificial surfaces have received the most attention, evidence also indicates that natural grass is a factor in injuries as well. This is particularly true when the field is not maintained properly. The classic 1974 study of high school injuries by Mueller and Blyth¹⁹³ reported a 30% reduction in the injury rate by resurfacing and maintaining the grass practice and game fields. Several studies of soccer, dance, and even ice hockey injuries have also indicated the playing surface as a factor.* One of the most important studies on the relationship between injuries and playing surfaces is that of Janda et al,¹²⁸ who found 70% of recreational softball injuries to be related to sliding into fixed bases. The follow-up to this study showed a 98% reduction in serious injuries with the use of breakaway bases (see Fig. 30-3).^127,129In running, hard surfaces and hills are seen as important factors in injuries, but few confirmatory studies have been done. The Ontario Cohort Study, one of the better epidemiologic studies of running injuries, found no relationship between surface and injury.²⁸⁸ A simultaneously reported 1989 study from South Carolina noted the only significant relationship between injuries and training surface to be in female runners running on concrete (Fig. 30-8).¹⁶³ Powell et al²²² examined the multiple etiologic factors involved in running injuries, including the running surface, and found little correlation. These studies have primarily examined injury from the standpoint of surface hardness. An alternate viewpoint is found in the European literature, where “eigen-frequencies,” or vibrational forces, from synthetic tracks are seen as a major factor in overuse problems in track athletes.¹¹ Haberl and Prokop¹¹⁰ have described this as “tartan syndrome,” a surface-related problem from “long-term non-physiologic stress, resulting in acute, chronic or periodical irritant states.” There is no conclusive evidence to confirm the exact importance of vibrational forces in running injuries.

In the analysis of athletic injuries to the lower extremities, the diligent clinician will develop knowledge of the injuries common to certain sports and the factors that play a role in their occurrence. Intrinsic and extrinsic factors must all be taken into consideration and form a matrix from which to assess the injured athlete, design a plan of treatment and rehabilitation, and ultimately to intervene where possible to alleviate the factors most likely to predispose the athlete to injury.

Differential Diagnosis

Many conditions must be considered when evaluating chronic leg pain in athletes, including but not limited to exertional compartment syndrome, medial tibial stress syndrome, stress fractures, gastrocnemius and other muscle strains, nerve entrapment syndromes, venous disease, arterial occlusion, fascial herniations, tendinitis, and radiculopathies (Table 30-2). From these many potential etiologies, the clinician must narrow the diagnosis through focused history taking and physical examination coupled with appropriate diagnostic tests. As in most circumstances in orthopaedics, knowledge of anatomy and physiology forms the background for understanding these diverse causes for leg pain in the athlete.

Incidence

Although it is difficult to assess the relative incidence of the various conditions that produce leg pain in the athletic population, it seems that about 25% relate to exertional compartment syndromes, 25% to stress fractures, and 25% to medial tibial stress syndrome or periostitis. This leaves a final 25% composed of an assortment of the less common causes, from radiculopathies to venous problems.329,420 Reviewing the literature on this subject leads to the conclusion that an accurate diagnosis is not always a certainty and coexisting pathologic entities may be more the rule than the exception. Up to 60% of patients with exertional leg pain have associated periostitis.^403,426 This periostitis corresponds most closely to the commonly used lay description for nonspecific exertional leg pain: shin splints. This has been used for the diagnosis in up to 15% of all running injuries in some studies.^373,387 Clearly, exertional leg pain is the source of many symptoms in the athletic population, and there is still ample opportunity for improving the accuracy of the diagnosis.

Chronic Exertional Compartment Syndrome

Diagnosis

Clinical Evaluation

Physical examination performed with the patient at rest is typically unremarkable. Usually some tenderness is noted over the affected compartment and over the middle to lower third of the tibia (from associated periostitis). Examination immediately after a period of exercise is often required to provoke the symptoms and expose the signs to the examiner. In this situation, tenderness over the affected muscle compartment and palpable firmness are more common. Muscle herniations through fascial defects are often discovered, but there is significant divergence of opinion on both their significance and incidence.317,399,404,409

The neurologic examination is usually uneventful, but signs of deep peroneal nerve compression (up to and including a foot drop) can occur when the anterior compartment is affected. Concurrent superficial peroneal nerve entrapment is common with lateral compartment syndrome and produces numbness or tingling into the dorsal foot. Arterial pulses should be checked and documented but are normal in CECS.

Radiologic Evaluation

Radiologic evaluation is warranted in all cases because stress fractures can mimic these symptoms and an occult tumor can be found even in an unlikely setting (Fig. 30-11). Lack of specific localized uptake on the technetium bone scan or no increase in signal on T2-weighted MRI images of the painful area effectively rules out a stress fracture.^339,354 MRI has gained increasing acceptance in the evaluation of chronic leg pain and compartment syndromes, with some advocating its use as a reliable, reproducible, and noninvasive diagnostic tool with no radiation exposure.^309,351,411

Figure 30-11 Radiographs are essential in evaluating leg pain in athletes; rare surprises like tumors may be discovered. A, Radiograph of stress fracture through benign cartilage tumor of tibia in a 9-year-old soccer player. B, Radiograph of aneurysmal bone cyst of fibula in 7-year-old child. C, Radiograph of osteosarcoma of distal tibia in active 16-year-old boy. (Courtesy John Murray, MD.)

Pressure Measurements

In general, the diagnosis of CECS can be made on clinical grounds. The syndrome can be confirmed with compartment pressure measurement.404,414,415 Although one would expect to have a certain agreed-on method and a specific pressure measurement for diagnosing compartment syndrome, this has not been the case. The suggested methods and the timing of the measurement have varied considerably.^{407,415,421,428} Box 30-1 lists the criteria we use. The test for exertional compartment syndrome can be performed quickly with a digital pressure monitor, but the physician should always be certain that the numbers are consistent with the clinical picture before deciding the treatment option (Fig. 30-12).

Box 30-1   Criteria for Diagnosis of Chronic Exertional Compartment Syndrome⁴⁰⁴

Mandatory

 Appropriate clinical findings

Secondary (At Least One)

 Compartment pressure ≥15 mm Hg before exercise

 Compartment pressure ≥30 mm Hg at 1 min after exercise

 Compartment pressure ≥20 mm Hg at 5-10 min

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