Running continues to be the exercise of choice for many individuals throughout the world. According to data received by USA Track & Field, in 2002, nearly 10.5 million Americans ran for more than 100 d. They estimate that 24.7 million Americans ran at least six or more times in the same year (usatf.org, April 1, 2011). Its convenience and low cost combined with growing interest in disease prevention make it a popular form of exercise. Although running has many known health benefits, it also poses significant risk for injury. van Gent et al. (40) conducted a systematic literature review of injuries in nonelite recreational and competitive long-distance runners. They reported lower extremity injury incidence varying from 19.4% to 79.3%, with the foot accounting for 5.7% to 39.3% of injuries. This article will discuss running injuries of the foot commonly encountered by the sports medicine physician. It also will touch briefly on barefoot (or minimal footwear) running because this recently has become a topic of interest among runners.
The sesamoid bones of the great toe are two seed-shaped bones embedded within the flexor hallucis brevis tendon. These bones play an important role in ambulation because they functionally lengthen the first ray during the late stance phase of gait to enable smooth lateral to medial weight transfer throughout the foot (Fig. 1). A bipartite or multipartite sesamoid occurs in 5% to 33% of the population (26). Most sesamoid injuries are due to overuse and include stress fracture (40%), sesamoiditis (chondromalacia, 30%), acute fracture (10%), osteochondritis (10%), osteoarthritis (5%), and bursitis (5%) (22). The tibial (medial) sesamoid is the larger of the two and is exposed to a greater weight-bearing load. This results in a higher risk of injury (9,16). Discovery of the precise tissue pathologic disease that causes the pain is often elusive.
Patients usually present with plantar medial forefoot pain when bearing weight. These patients may walk on the lateral side of the foot as a strategy to avoid pain. Examination reveals significant tenderness and perhaps swelling over the sesamoid bones. Plantar pain with passive dorsiflexion of the great toe accompanied by weakness or pain with resisted plantarflexion is a nonspecific clue to sesamoid problems. Radiographs often are unremarkable but may reveal an acute fracture, arthritic changes, and/or malalignment (9). As previously stated, a bipartite sesamoid is present nearly 30% of the time. If present, symptoms cannot be attributed to a bipartite sesamoid strictly on the basis of radiographic findings. If a sesamoid pathologic abnormality is suspected, radiographs should include anteroposterior, lateral, and sesamoid views. The latter view is comparable to a Merchant's view of the knee. If radiographs are nondiagnostic, a bone scan or magnetic resonance imaging (MRI) can help differentiate a bipartite sesamoid from an acute or stress fracture (26).
Initial treatment of sesamoid problems begins by unloading the first metatarsophalangeal joint. This may be as simple as restricting impact activity. A metatarsal pad or bar or an orthotic with a first metatarsophalangeal cutout may be sufficient to limit pain from everyday walking. If pain persists, a non-weight bearing period is warranted. The duration varies, although it usually is continued until tenderness resolves. At this point, a careful and gradual return to activity is spread over several weeks. If pain becomes an ongoing issue, a corticosteroid injection may be an additional treatment option (9). Early detection of sesamoid stress fractures is paramount. A 6-wk non-weight bearing period is necessary because these fractures are at an increased risk for nonunion. If pain persists and all conservative measures fail, surgical intervention should be considered. There are several surgical options, including partial sesamoidectomy, complete sesamoidectomy, and bone grafting of a sesamoid nonunion (9). There are, however, potential long-term biomechanical consequences (8). It is therefore important that the consulting surgeon have experience with these injuries and their complications. Biedert and Hintermann (4) reported five athletes treated with partial sesamoidectomy for nonhealing stress fractures, all of whom returned to play within 6 months. Saxena and Krisdakumtorn (31) also reported successful return to sport after a sesamoidectomy in a small cohort of patients.
Metatarsal Stress Fractures
Metatarsal stress fractures or "march fractures" originally were described in 1855 by Breithaupt, a Prussian Army doctor, who reported painful swollen feet in soldiers after long marches (16). Metatarsal stress fractures are the second most common stress fracture in athletes and the most common in the foot (11). During running, the plantar musculature of the toes helps dissipate the stress on the metatarsals. Muscular fatigue during strenuous or prolonged running imparts increased stress to the metatarsals (41,44). The second, third, and fourth metatarsals account for 90% of fractures (26). The second metatarsal in particular is vulnerable to injury because it is recessed and is encompassed more rigidly by the cuneiforms. This anatomic rigidity restricts motion and predisposes to excessive bending forces, resulting in a higher incidence of bone stress injuries (26,41). The bending strain on the second metatarsal has been reported as 6.9 times greater than that on the adjacent first metatarsal (41). As with most stress fractures, metatarsal stress fractures frequently occur with a change in running frequency, intensity, or duration. Pes planus foot type may increase the risk for metatarsal stress fractures (26).
Patients usually present with forefoot pain of insidious onset. Initially, the pain is relieved by rest. If running continues, pain becomes unremitting, until it affects activities of daily living. Usually this occurs a few weeks after a sudden change in training, but it may occur even after a single, more intense run (16).
Examination reveals focal tenderness over the affected metatarsal and sometimes reveals dorsal forefoot swelling. This subtle edema can be appreciated best by comparing the skin over the extensor tendons of both feet simultaneously. The swelling will obscure the normally well-defined tendons. Axial loading of the metatarsal shaft by dorsiflexing the proximal phalanx to expose the metatarsal head and then applying a force down the shaft can elicit pain due to a stress fracture. Resisting active extension of the toes can help differentiate a stress fracture from tendinitis, because this should be painful with tendinitis but not with a stress fracture (26).
Results of radiographs ordered within the first few weeks of onset of pain often are normal. Later, a visible bony callus forms, indicating a healing fracture site, although features in radiographs can remain normal despite MRI or bone scan confirmation (16). Banal et al. (1) proposed musculoskeletal ultrasound as an additional imaging modality for diagnosing stress fractures. Even with a negative radiographic result, history and physical examination usually are diagnostically sufficient and the most cost-effective strategy for management (7). If circumstances warrant an urgent definitive diagnosis, an MR image should be obtained (19).
Initial treatment involves rest from running. If there is pain with walking, use of a postoperative shoe or walking boot may be implemented with full or partial weight bearing. Progression to full weight bearing and weaning from the appliance can occur as pain allows. Running should be restricted for 4 to 6 wk or until the patient is free of pain during daily activities for 2 wk (11). Return to running should be gradual to avoid recurrence of injury. A biomechanical examination may be helpful in identifying risk factors for metatarsal stress fractures. Custom orthosis or other accommodative orthotic devices may help in these situations (8,26).
Navicular Stress Fractures
Navicular stress fractures were reported first in 1970 by Towne et al. (37). They are found most commonly in track-and-field athletes, among jumpers, hurdlers, sprinters, and middle-distance runners. They also may be found in endurance runners (13). Unfortunately, these injuries frequently remain undiagnosed for months because they commonly present with subtle and vague findings (18). The navicular bone is situated uniquely in the midfoot, articulating with the talus, all three cuneiforms, and the cuboid. It plays an integral part in a number of joints, is subject to significant forces, and possesses an unusual blood supply. These factors render it susceptible to stress injury. Investigators have described an area of significant shear stress through the central third of the navicular body. This shear stress, coupled with a decreased vascular supply to this area, makes this the most common region of injury and subsequent poor healing (21).
Patients classically present with a history of insidious-onset, vague, intermittent, dorsal midfoot pain during activity. Early on, this pain may subside with rest. The pain progresses, often necessitating rest from running. This history should prompt the examiner to carefully palpate the apex of the navicular or the "N" spot, as coined by Khan (18). If palpation reveals tenderness at this location, navicular stress fracture should be assumed until proven otherwise.
Imaging should begin with radiography, the results of which usually are normal. Further diagnostic workup should include a bone scan, a computed tomography (CT), or an MRI. MRI or bone scanning can determine current bone stresses, whereas CT is better at characterizing the exact nature and extent of these fractures (21).
Treatment options vary by fracture type, CT-identified modifiers, the athlete's need to return to sport, and the clinician's preference. A recent meta-analysis by Torg et al. (36) looked at conservative versus surgical treatment for both complete and incomplete navicular stress fractures. Results revealed that non-weight bearing management yielded 96% successful outcomes. Surgical management yielded 82% successful outcomes. Results did not show a statistically significant difference between the two strategies, but both were significantly superior to weight bearing management. If conservative management is elected, then it should entail 6 to 8 wk of strict, immobilized non-weight bearing. Some suggest taking the cast off at 6 wk and, if tenderness at the N spot persists, then maintaining non-weight bearing for an additional 2 wk (8,21). Return to activity should be gradual and without additional symptoms. Average period of return to activity is 5.6 months (11). The lengthy recovery should be discussed in advance with the patient to avoid unrealistic expectations. If symptoms return or persist, then running should cease, and subsequent imaging should be considered.
The plantar aponeurosis is a nonelastic fibrocartilaginous structure originating at the calcaneal tuberosities and inserting broadly into each of the proximal phalanges (3). The characteristic pain of plantar fasciitis involves the inferomedial aspect of the calcaneus and is intensified with the initiation of weight bearing. Symptoms often abate after the first few moments of ambulation or running, but the pain returns after completion of the activity and subsequent rest.
Plantar fasciitis has been reported to be present in approximately 7.9% of runners with a musculoskeletal problem (35) and has a lifetime prevalence as high as 10% (29).
There is no clear etiology yet published and agreed on, but its development is thought to have a mechanical origin (14,28,43).
In normal running gait, the foot transforms from an accommodating landing pad on heel strike to a rigid lever for propulsion. This change is accomplished passively by a windlass mechanism in which toe dorsiflexion during heel liftoff pulls the plantar fascia taut. This shortens and mechanically locks the midfoot, attempting to prevent the longitudinal arch from collapse. This assists propulsive energy transfer from the gastrocnemius-soleus complex to the forefoot.
Pes planus foot structure, excessive pronation (43), decreased ankle dorsiflexion, increased daily time spent bearing weight, and obesity (29) have been described as risk factors for developing plantar fasciitis. The diagnosis is made clinically on the basis of history and physical examination. Plain radiographs can be helpful in excluding other diagnoses and may show the presence of a plantar calcaneal spur. This finding is nonspecific because, although it is present in approximately 50% of patients with plantar fasciopathy (10), it also is present in 15% to 27% of the asymptomatic population (14). Ultrasonography of the plantar heel also has been described as a useful diagnostic modality. Increased thickness of the plantar fascia (>4.0 mm) immediately distal to the calcaneal enthesis and hypoechogenicity within the proximal fascia are characteristic findings in plantar fasciopathy (38).
The natural progression of this disease is self-limited and often resolves within 1 year in 80% to 90% of patients (14,26,34). Numerous treatments have been studied and reported in the literature, but no one therapy has demonstrated superiority. Reviews of controlled trials have shown that taping, chiropractic manipulation, therapeutic ultrasound, and laser therapy confer little, if any, benefit in plantar fasciitis treatment (34,39). Stretching and use of corrective orthotic devices show differing results in the literature, with some studies showing moderate benefit and others showing none (34). An intralesional corticosteroid injection can be considered, but this is often a short-term benefit and is associated also with a mild risk of plantar fascia rupture (26). Platelet-rich plasma injections have been described also, but evidence for their efficacy has yet to be reported (27).
Surgery should be considered only for patients with recalcitrant plantar fasciitis who have exhausted conservative therapy. Full or partial release of the plantar fascia is the most common surgical intervention, but others, including calcaneal osteotomy, have been described as well (24).
Because no single conservative therapy has been demonstrated to be clearly superior to all others, reasonable first-line treatment should be of low risk and low cost. Consideration should be given initially to plantar fascia/Achilles tendon stretching, patient education, and possibly prefabricated or custom orthotic devices.
Tendinopathies of the Midfoot and Forefoot
Tendinitis of the common extensor tendon of the forefoot often occurs secondary to an acute alteration in mechanics. Its presence in runners should prompt an inquiry regarding any recent increase in hill running. Demand on the tibialis anterior muscle increases with uphill running because it must provide increased dorsiflexion of the foot during a swing phase to achieve ground clearance. During downhill running, the extensor tendons experience a longer and more rapid eccentric loading during the brief interval from heel contact to midstance phase of gait. Running on an unstable surface such as snow or ice also may predispose a runner to extensor tendinitis because the stride length is shortened to increase stability, and the swing foot then must increase dorsiflexion to maintain ground clearance (26). Ill-fitting shoes or shoes laced too tightly also may limit normal tendon gliding.
Findings from a physical examination may range from very minimal to extensive dorsal foot tenderness, crepitance, and swelling. Passively stretching the tibialis anterior tendon in plantarflexion, eversion, abduction, and pronation also may elicit pain in the anterior ankle or dorsum of the foot (2). The course usually is self-limited and often responds quickly to rest, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs) with rare need for immobilization (33). A shoe lacing technique that skips an eye may reduce direct pressure over the extensor tendons because they cross a sometimes prominent tarsometatarsal joint.
The flexor hallucis longus (FHL) originates in the posterior leg along the fibula and the interosseous membrane. It proceeds through a fibroosseous tunnel posterior to the ankle, intersects with the flexor digitorum longus (forming the knot of Henry) in the midfoot (Fig. 2), proceeds past and deep to the sesamoids, and then inserts at the base of the first distal phalanx. This coursing of the FHL makes it a strong hallucal and ankle plantar flexor. FHL dysfunction is overrepresented in ballet dancers, likely secondary to repetitive hyper-plantar-flexed posturing (en pointe) (23). Tenderness elicited with palpation along the course of the tendon or pain evoked with resisted great toe plantarflexion is compatible with tendinitis. Conservative treatment usually is successful and consists of rest, icing, NSAIDs, and addressing any provocative factors (26). Athletes who fail conservative therapy should undergo further investigation for the possibility of a stenosing tenosynovitis, occasionally requiring surgical correction.
Posterior Tibial Tendinitis
The tibialis posterior muscle arises in the deep posterior compartment from the proximal third of the tibia, fibula, and interosseous membrane. It courses immediately posterior to the medial malleolus and then splits, providing two different insertions. The first is directed to the navicular tuberosity, the inferior capsule of the medial cuneiform joint, and the plantar surface of the medial cuneiform. The second portion inserts into the inferior surfaces of the middle and lateral cuneiforms and into the bases of the associated metatarsals. It functions as an inverter of the foot and as a midfoot dynamic stabilizer (12). The posterior tibial tendon (PTT) acts as a muscular support to the medial longitudinal arch and thus is loaded eccentrically as the foot transitions from a relatively supinated heel strike to a relatively pronated midstance position. PTT dysfunction is more often a greater concern for the older patient with comorbidities such as obesity, hypertension, and diabetes. However, it may afflict the runner. Inadequate footwear, an overpronating foot, and changes in training regimen can all serve as potential instigators of posterior tibial tendinitis (26). Pain often will be the patient's iatrogenic stimulus, and examination may elicit tenderness along the course of the tendon or with resistance of foot inversion. Chronic dysfunction of the PTT is a separate entity denoted by valgus hindfoot deformity, increased pronation, abduction of the forefoot, and flattening of the longitudinal arch (45). Acute mild tendinitis often can be managed conservatively with NSAIDs, icing, and appropriate rest. For patients with more significant pain and dysfunction, temporary immobilization is recommended (33). Although uncommon, PTT ruptures can occur. They should be treated with non-weight bearing immobilization, and surgical consultation should be sought (26).
The fibularis (peroneus) longus and fibularis brevis muscles originate from the lateral compartment of the leg. Their tendons traverse together through a common sheath posterior to the fibula, and then, at the distal ankle, the tendon sheath bifurcates. The brevis muscle continues and inserts into the tuberosity of the fifth metatarsal. The longus muscle courses medially, passing between the long plantar ligament and the cuboid groove, aiming for its insertion into the base of the first metatarsal and the lateral portion of the medial cuneiform.
When not bearing weight, the peroneal muscles function jointly as plantar flexors of the ankle, but their main function lies in hindfoot eversion. In addition, the longus is an open-chain plantar flexor of the first ray. This translates to a closed-chain plantarflexion stabilizer of the first ray (32).
Peroneal tendinitis often occurs after initiation of novel, prolonged, or repetitive activity (15). Chronic lateral ankle instability, cavovarus hindfoot alignment, and ankle inversion injuries also are associated with its development (15). Examination should assess for hindfoot malalignment, swelling along the tendon sheath over the lateral foot and leg, and crepitation, tenderness, or mass on palpation over the tendon (30). Diagnosis is made clinically, but radiographs can be helpful to rule out other possible diagnoses and to identify an os peroneum, present in 20% of the population (42). An MR image or an ultrasonograph demonstrating tendon thickening or fluid within the tendon sheath is suggestive of peroneal tendonitis (15). First-line treatment is conservative and consists of activity modification, NSAIDs, rest, physical therapy, and, possibly, immobilization. A lateral heel wedge also may be considered. For tendinopathy exacerbated by an accessory ossicle, intratendinous sheath corticosteroid injection is a reasonable treatment option. Anecdotally, this entity seems quite painful, but, fortunately, it resolves more quickly than some of the other tendinopathies subject to chronicity.
Endurance running is a locomotive means uniquely human among bipedal primates (5). Although its contribution to daily survival is less important for present-day men versus early hominids, it continues to be a popular form of recreation. Participation in marathons in the United States increased by 9.9% in 2009 and then again by 8.6% in 2010, totaling approximately 507,000 runners completing marathons in that year (State of the Sport Report, runningusa.org, April 1, 2011).
Bramble and Lieberman (5) have proposed that endurance running, first believed to be present in the genus Homo, was a means of hunting or scavenging for protein-rich resources. It even may have been a means to run down mammals to death from exhaustion.
Historically, humans have run barefoot or with minimal footwear such as sandals or animal skins. The introduction of the modern running shoe in the 1970s coincided with an increase in the number of participants in endurance running. In developed countries today, shod endurance runners far outnumber their minimal-footwear or barefoot counterparts. Lately, a debate over the benefits of barefoot versus shod running has emerged because there has been a growing subset of the population reverting to minimal-footwear running.
Recent studies have sought to examine the kinematics of the barefoot endurance runner versus the shod (6,17,20). Foot strike in all runners occurs in one of three different manners: rear foot strike (RFS, heel lands first), midfoot strike (heel and ball of the foot land simultaneously), and forefoot strike (FFS, ball lands first then heel).
Significant differences in the mechanics of barefoot versus shod runners have been described. Most notable is that habitually shod runners predominantly perform RFS, whereas barefoot runners are more likely to perform midfoot strike or FFS. Shod RFS runners experience an impact with the ground (ground reaction force) that is absorbed over a shorter time than that experienced by FFS runners. Running shoe manufacturers attempt to mitigate this force with increased cushioning of the heel sole in footwear. In contrast, FFS runners absorb the impact in a toe-heel-toe gait manner that converts translational energy into a rotational force about the ankle as it loads the Achilles tendon and the ankle plantar flexors. Rates of loading in FFS barefoot runners have been measured at approximately half of those in RFS shod runners (20). This longer period of absorption reduces the effective magnitude of the impact force (25).
An FFS requires a shorter stride length than RFS does and, therefore, an increased cadence to maintain the same running speed. This increased number of foot strikes per given distance has important implications for the energy cost of barefoot endurance running. Even if one running pattern is shown to be less injurious than the other, it remains uncertain whether endurance runners are able to change gait styles without undue consequence. In addition, if humans transition to barefoot running on the basis of an argument of origins, then we also must take into account the divergent motives behind endurance running in early hominids versus present-day men.
Although data examining the biomechanics of the two groups exist, thus far, there are virtually no data investigating the difference in injury incidence between barefoot and shod runners. Prospective studies observing injury patterns in both populations are needed.
The popularity of running continues to grow, leading to increased numbers of injuries presenting to sports medicine offices. The clinician must maintain a high level of suspicion and awareness of which injuries necessitate withdrawal from sport and which allow for continued participation. This will aid in avoiding misdiagnoses and delays in diagnosis that can lead to unfortunate long-term sequelae.
The authors did not receive funding from any institution.
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