Running injuries of the lower extremities: Patient evaluation and common conditions

INTRODUCTION — Running is one of the world's most popular forms of exercise with millions of regular participants. In the United States alone, up to 40 million people run regularly, with more than 10 million running at least 100 days per year [1]. Although running is an effective way to achieve many health benefits, it is associated with a high risk of injury; yearly, up to one-half of runners report an injury [2]. Although some injuries are traumatic, most are due to overuse.

Given the popularity of running and the high rate of associated overuse injuries amenable to nonsurgical management, the primary care clinician is likely to manage many injured runners and should be familiar with the diagnosis and treatment of common problems. Evaluation of the injured runner and descriptions of common injuries and conditions sustained by runners are discussed here. The epidemiology, risk factors, and methods for preventing running-related injuries are reviewed separately. (See "Running injuries of the lower extremities: Risk factors and prevention".)

Stand-alone topics devoted to specific lower extremity injuries are found separately, including those listed here:

●Knee and upper leg conditions (see "Patellofemoral pain" and "Iliotibial band syndrome" and "Hamstring muscle and tendon injuries" and "Quadriceps muscle and tendon injuries")

●Ankle conditions (see "Ankle sprain in adults: Evaluation and diagnosis" and "Achilles tendinopathy and tendon rupture" and "Syndesmotic ankle injury (high ankle sprain)")

●Foot conditions (see "Plantar fasciitis" and "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults" and "Evaluation, diagnosis, and select management of common causes of midfoot pain in adults")

●Stress fractures (see "Stress fractures of the metatarsal shaft" and "Stress fractures of the tarsal (foot) navicular" and "Stress fractures of the tibia and fibula")

Medical conditions associated with running and other aspects of aerobic exercise are reviewed separately:

●Cardiovascular conditions (See "Athletes with arrhythmias: Clinical manifestations and diagnostic evaluation" and "Athletes: Overview of sudden cardiac death risk and sport participation".)

●Exercise and health (See "The benefits and risks of aerobic exercise" and "Exercise prescription and guidance for adults" and "Exercise for adults: Terminology, patient assessment, and medical clearance".)

EVALUATION OF THE INJURED RUNNER

History — Evaluation of the injured runner begins with a thorough history, which should include inquiries about:

●Prior injuries and related treatments (including the runner's compliance with treatment)

●Current training patterns, including mileage, frequency, intensity, and training methods (eg, hill running) as well as changes in training that preceded the injury

●Shoe and orthotic use, including any recent change in shoes (See "Running injuries of the lower extremities: Risk factors and prevention", section on 'Running shoes'.)

●Training surface, including any recent change

●Injury details (eg, what provokes and reduces symptoms, duration of symptoms)

●Athletic activities other than running

●Detailed training history, including running and racing experience

●Medical conditions and prior surgeries

●Medication and supplement use

●Diet, especially any dietary restrictions or recent weight loss (see "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations", section on 'Female athlete triad' and "Overtraining syndrome in athletes", section on 'Low energy availability-relative energy deficiency')

Physical examination — Examination of the injured runner includes assessment of not only the injured area but of all related structures (ie, the runner's entire "kinetic chain"), noting any imbalances or deficits in structure (eg, leg length discrepancy (picture 1)), strength, flexibility, or motion (table 1). Discrepancies may exist between legs or between muscle groups of the same leg (eg, hamstrings disproportionately stronger than quadriceps). One way to organize each element (eg, observation, strength testing) of the physical examination is to begin with proximal structures (eg, spine and pelvis) and work distally.

Careful observation of the patient's walking and running gaits helps to confirm that the anatomic problems identified during a stationary examination affect biomechanical performance. (See "Clinical assessment of walking and running gait".)

Begin your assessment by asking the injured runner to stand in front of you, noting their posture and lower extremity alignment. Observe the legs from hip to foot, looking for symmetry. Ask the patient to stand on one foot and then the other, watching for balance, control, and posture. Does the unsupported hip sag (ie, positive Trendelenburg test) (picture 2 and picture 3)? A positive Trendelenburg test suggests weakness of the gluteus medius, a common finding in runners with hip and knee pain.

Note the structure of the knee, especially genu varus (picture 4) (which may be associated with iliotibial band syndrome or medial meniscal pathology) or valgus (picture 5) (often seen in females with patellofemoral pain). Note the position of the patella and any apparent muscular asymmetry.

Make note of foot structure and position. Does the runner have a normal, high (picture 6), or flat longitudinal arch (picture 7 and picture 8)? Note the position of the calcaneus. Does the runner have calcaneal valgus (picture 9) or varus? Does the runner have splaying (picture 10), hammering (picture 11), or other toe abnormalities? Ask the patient to walk and to squat. Watch for a limp, stiffness of one limb, and a tendency to shift weight off one limb.

Screen for tenderness and altered mobility of the spine, pelvis (including sacroiliac joints), hips, knees, ankles, and feet before turning your attention to the area of complaint. Be sure to assess muscle strength and neurovascular status throughout the lower extremity. Weakness of the hip musculature (particularly hip abductors) is common among novice runners, frequently contributing to lower extremity pain, especially patellofemoral pain. (See "Patellofemoral pain".)

The following findings – moving distally from lumbar spine to foot – may be noted during the examination:

●Lower back and abdomen

•Increased lumbar lordosis suggests weak anterior core muscles, a common condition in runners with hip weakness.

•Loss of normal lumbar lordosis (picture 12) (with or without back pain) is often present with tight hamstrings.

●Hip and groin

•Hip flexion, rotation, or abduction weakness is present with many lower extremity injuries, particularly those affecting the hip or knee.

•Loss of internal rotation of the hip (picture 13) occurs with femoral neck stress fracture.

•Pain and/or a sense of "catching" in the groin with the knee flexed to 90 degrees suggests a labral tear but also may be seen with iliopsoas tendinopathy.

●Thigh and knee

•Leg length inequality (picture 1) may be present with stress fractures and possibly with iliotibial band syndrome and lower back and pelvic injuries.

•Vastus medialis atrophy or asymmetry can occur with patellofemoral pain or in athletes who have had knee surgery.

•Asymmetry of the quadriceps muscles is common in runners with osteoarthritis of the hip.

●Lower leg

•Tenderness along the medial tibial border bilaterally is often present with medial tibial stress syndrome (MTSS), or "shin splints."

•Localized tenderness along the tibial border and a positive hop test suggest a tibial stress fracture.

●Foot and ankle

•Achilles tendon thickening or nodules suggests Achilles tendinopathy.

•Tenderness at the medial insertion of the plantar fascia into the calcaneus (picture 14) suggests plantar fasciitis.

•Hallux limitus (picture 15) or hallux rigidus (picture 16) and reduced ankle dorsiflexion can develop with plantar fasciitis or calf muscle injuries.

•Splayed toe sign (picture 10) and forefoot widening can occur with metatarsalgia.

Diagnostic imaging, including plain radiographs, ultrasound, magnetic resonance imaging (MRI), computed tomography (CT), and bone scan may be necessary in some cases to make a definitive diagnosis. However, the clinician should have a clear differential diagnosis in mind before ordering such studies.

Once a diagnosis is made and a treatment plan established, the clinician and athlete should work together to uncover and eliminate potential contributing factors, as many running injuries appear to be multifactorial. The mainstay of treatment for the vast majority of running injuries is "relative rest," which means stopping running (or, at a minimum, significantly reducing mileage) while the injury heals. Depending upon the injury, most runners can maintain reasonable conditioning by performing non-impact exercises in a pool or on a bike or by using other equipment (eg, rowing machine).

SPECIFIC INJURIES

Hip injuries

Overview and approach — Hip injuries are less common in runners than injuries to the lower extremity, and they can be difficult to diagnose. Nevertheless, during jogging, the hip joint is subjected to loads up to eight times body weight, and both acute and chronic injuries can occur [3]. In runners, the differential diagnosis of hip pain includes gluteus medius tendinopathy, piriformis syndrome, stress fracture of the femoral neck, labral tear, and, less often, radicular pain from the lumbar spine. Better understanding of the functional anatomy of the hip suggests a correlation between hip muscle weakness and injury to the low back or lower extremity in athletes, including runners [4-6].

Gluteus medius weakness and tendinopathy and piriformis syndrome — The gluteus medius originates along the external surface of the ilium and runs distally and laterally to its attachment on the greater trochanter of the femur (figure 1). The gluteus medius abducts the hip and assists with pelvic stability during running. Weakness of the muscle typically causes pain with hip abduction and rotation. Pain generally increases when the muscle is stretched, and there may be focal tenderness at the muscle's insertion, just medial and superior to the greater trochanter. Difficulty maintaining a level pelvis while standing on one leg (positive Trendelenburg sign) may be noted (picture 2).

The piriformis muscle is a small but important external rotator of the hip that crosses the sciatic nerve and is believed by some to cause sciatica-type pain when it compresses the nerve (figure 2) [7,8]. However, the existence of this so-called "piriformis syndrome" remains controversial, and diagnosis is difficult [9-11]. Piriformis syndrome in the runner may be associated with foot overpronation, weakness of the gluteal muscles and other hip abductors, and tightness of the hip adductors.

The mainstay of treatment for both gluteus medius tendinopathy and piriformis syndrome is physical therapy and correction of biomechanical abnormalities. Orthotics and massage therapy may be useful; acetaminophen and nonsteroidal antiinflammatory drugs may be used for analgesia. There are reports of using injections of local anesthetics, glucocorticoids, and botulinum toxin (Botox) to treat piriformis syndrome [12].

Femoral neck stress fracture — Stress fractures of the femoral neck are an uncommon but important cause of hip or groin pain in the adult runner because of the relatively high risk of nonunion. (See 'Stress fractures' below and "Femoral stress fractures in adults".)

Labral tear — The acetabular labrum is a ring of fibrocartilage and dense connective tissue attached to the bony rim of the acetabulum. It is thought to be largely avascular. Although the labrum's function is not fully understood, it is thought to provide stability and decrease the stress placed on the hip joint. Therefore, a significant tear in the labrum can increase stress on the hip joint, decrease stability, and ultimately lead to damage of the articular cartilage.

Labral tears are reported in sports that require frequent hip rotation, such as soccer and hockey, and in runners, especially female runners. Runners with a labral tear typically complain of pain in the anterior hip or groin. They may have mechanical symptoms, including clicking, locking, catching, or giving way (so-called "snapping hip"). Other hip injuries that may produce such mechanical symptoms include iliopsoas tendinopathy.

Labral tears are complex and often frustrating to treat. Physical therapy has mixed results. Arthroscopic surgery is often helpful, but the recovery can be prolonged. Runners diagnosed with labral tears should be counseled carefully regarding the paucity of evidence for determining the best treatment and the benefits and risks of each approach.

Iliopsoas tendinopathy — Iliopsoas tendinopathy produces symptoms similar to a labral tear but presents more often as anterior hip pain in younger athletes, especially after a rapid growth spurt, and is more easily treated. Athletes who repeatedly engage in forceful flexion of the hip, including track and field athletes (eg, hurdlers, jumpers), are at greatest risk. Examination usually reveals tight, painful hip flexors (picture 17 and figure 3). Iliopsoas tendinopathy typically responds within a few weeks to activity modification, acetaminophen and nonsteroidal antiinflammatory drugs, and physical therapy.

Knee and thigh injuries

Knee pain (patellofemoral pain) — Knee pain is among the most common complaints from runners. Most such runners are diagnosed with patellofemoral pain (PFP). Despite the prevalence of this diagnosis, no consensus exists about its etiology or the factors most responsible for causing pain. Overuse and malalignment are commonly cited causative factors. In addition, runners (especially females) with PFP often have decreased strength in hip abduction, external rotation, and extension compared with healthy controls. Patients with PFP typically complain of anterior knee pain that worsens with squatting, running, prolonged sitting, or ascending or descending steps. Pain is often poorly localized "under" or "around" the patella. Details about the diagnosis and management of PFP are provided separately. (See "Patellofemoral pain".)

Iliotibial band syndrome — The iliotibial band (ITB) consists of connective tissue that runs from the ilium to the anterolateral aspect of the proximal tibia (picture 18 and figure 4). It is involved in hip abduction and internal rotation as well as knee extension and flexion, and it helps to stabilize the knee during running.

The ITB syndrome (ITBS), which occurs primarily in runners, is characterized by an aching or burning pain at the site where the ITB courses over the lateral femoral condyle; occasionally, the pain radiates up the thigh toward the hip. Runners often complain of such lateral knee pain while running, but pain may persist after training, especially with activity that requires repetitive flexion and extension of the knee, such as ascending or descending stairs or standing from a seated position. The diagnosis of ITBS is clinical; no imaging is typically needed. A detailed discussion is provided separately. (See "Iliotibial band syndrome".)

Hamstring injuries — Hamstring injuries are typically acute; the injured runner complains of developing a sudden, sharp pain in the posterior thigh while running at high speed or up hills (picture 19 and figure 1). Examination findings depend upon the severity of injury and may include a limping gait (due to the inability to fully extend the knee), ecchymosis, a visible or palpable defect in the hamstring muscle, focal tenderness, and pain or weakness with muscle contraction. Details about the diagnosis and management of hamstring muscle injuries are provided separately. (See "Hamstring muscle and tendon injuries".)

Knee and hip osteoarthritis — Exercise is recommended for most patients with osteoarthritis of the hip or knee. Although water-based exercise is often suggested, multiple studies confirm the value of regimens involving full weightbearing exercise. (See "Management of knee osteoarthritis", section on 'Exercise'.)

Despite this evidence, many clinicians subscribe to the traditional teaching that patients with osteoarthritis of the knee or hip should not run because it exacerbates the condition. However, the medical literature does not support the contention that running contributes to the degeneration of articular cartilage, or that running increases knee pain in runners with knee osteoarthritis [13-16]. A systematic review of 15 studies on the relationship between running and osteoarthritis noted that while available evidence is too limited to reach definitive conclusions, it suggests no association between the two [15]. Therefore, we believe it is reasonable, and possibly advantageous, for runners with mild or moderate knee or hip osteoarthritis to continue moderate levels of running, using pain and function to guide the volume of activity.

Representative studies of the relationship between running and osteoarthritis include the following:

●A large follow-up study using questionnaires completed by established cohorts of runners and walkers reported reduced risk among runners for developing osteoarthritis or requiring hip replacement surgery compared with those participating in other exercise [14]. Risk dropped substantially in those who ran ≥12.9 km/week (8 miles/week). The authors attribute much of the effect to the lower body mass index among runners.

●A systematic review of over 114,000 subjects reported a lower prevalence of hip and knee osteoarthritis in recreational runners (3.5 percent) compared with sedentary controls (10.2 percent) [17]. However, competitive runners with longer exposure to high-volume running had a higher prevalence of osteoarthritis (13.3 percent).

●A prospective cohort study followed 45 runners and 53 controls over 18 years and, using a validated score to assess for osteoarthritis, found no difference between the two groups in the progression or the number of severe cases of knee osteoarthritis [16].

●An observational cohort study of 1203 individuals with knee osteoarthritis, of whom 138 were runners, found that self-selected running was associated with improved knee pain and no difference in radiographic progression of knee osteoarthritis compared with non-runner controls [18].

●Several small prospective and retrospective studies have reported no evidence of premature damage of articular cartilage or increased risk for osteoarthritis among long-distance runners [19-22].

●Small clinical and laboratory studies using magnetic resonance imaging (MRI) to evaluate the knees of long-distance runners report no significant damage to articular cartilage following a race and no major differences when images were compared with those of active non-runners [23-25].

Stress fractures — Stress fractures in runners occur most often in the tibia but can develop in any bone of the lower extremity, including the metatarsals, navicular, and femoral neck [26]. Detailed discussions of stress fractures, including a description of those at high risk for nonunion, appear separately; a brief description and information of particular importance for runners are provided here. (See "Overview of stress fractures" and "Stress fractures of the tibia and fibula" and "Stress fractures of the metatarsal shaft" and "Femoral stress fractures in adults" and "Stress fractures of the tarsal (foot) navicular".)

When evaluating the runner with a suspected stress fracture, the clinician should ask for a description of the pain, running patterns and recent changes in training, shoe and orthotic wear, and prior injuries. Information about the patient's nutrition and menstrual history, and any family history of metabolic bone disease, are also important.

Typically, the runner with a stress fracture complains of focal pain that is insidious in onset, increases as a run progresses, and improves with rest. Over time, if the athlete persists in running despite such symptoms, pain occurs with less strenuous activity and ultimately at rest. Some runners present with acute onset of severe pain, which may result from a complete fracture at the site of a pre-existing stress fracture.

Important risk factors for developing stress fractures include a history of prior stress fracture, increasing volume and intensity of training, poor running biomechanics, female sex and menstrual irregularity, a diet poor in calcium, and poor bone health [27]. The management of stress fractures in runners is discussed separately. (See "Overview of stress fractures", section on 'Treatment concepts'.)

The clinician should be aware that stress fractures at high risk for nonunion (eg, femoral neck and navicular) are more common in runners than in other athletes. If a high-risk stress fracture is suspected, an aggressive workup (including advanced imaging if necessary) is warranted, and immediate orthopedic consultation should be obtained if the diagnosis is confirmed. A history of recurrent stress fracture or a fracture in cancellous bone suggests that the runner's bone mineral density may be low and should be measured. (See "Screening for osteoporosis in postmenopausal women and men".)

Femoral neck stress fractures should be suspected in any distance runner with groin pain of insidious onset (image 1), especially female distance runners at risk for relative energy deficiency in sport, which can lead to low bone mineral density. The condition has been referred to as the "female athlete triad" (osteopenia, eating disorder, amenorrhea). A fulcrum test may be positive (picture 20). (See "Femoral stress fractures in adults" and "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations".)

Navicular stress fractures occur more often in male athletes participating in track and field events (eg, hurdlers, jumpers, sprinters) and middle-distance runners [26]. The athlete with a navicular stress fracture often presents with insidious pain in the midfoot or arch (picture 21 and picture 22) that increases with jumping. (See "Stress fractures of the tarsal (foot) navicular".)

Medial tibial stress syndrome (shin splints) and tibial stress fractures — Clinicians confronted by runners with shin pain must distinguish between stress fractures of the tibia and medial tibial stress syndrome (MTSS), often referred to as "shin splints." Although the history may be similar, a focal, palpable area of tenderness is present in most patients with stress fractures, whereas tenderness is much more diffuse and there are no discrete palpable lesions in those with MTSS. Imaging may be necessary in some cases to rule out a stress fracture. Plain radiographs are normal in patients with shin splints but may also be unrevealing early in the course of a stress fracture. (See "Stress fractures of the tibia and fibula", section on 'Clinical presentation and examination' and "Stress fractures of the tibia and fibula", section on 'Diagnostic imaging'.)

Distinguishing between the two diagnoses affects treatment. A runner with a stress fracture should avoid running and pursue nonimpact activities like swimming or cycling while the stress fracture heals, while the runner with MTSS can continue running but should reduce the total mileage. A systematic review found that shock-absorbing insoles may reduce symptoms and prevent recurrence of MTSS [28]. Risk factors may include obesity and limited mobility of the ankle and hip [29].

Chronic exertional compartment syndrome — Chronic exertional compartment syndrome (CECS) occurs when increased pressure within a muscle compartment reduces blood flow, leading to muscle ischemia and pain when metabolic demands cannot be met. The patient with CECS is often a young runner who describes gradually increasing pain in a specific muscle region (usually the lower leg) during exertion. The pain may be described as aching, squeezing, cramping, or tightness. Pain generally begins within several minutes of starting a run, often at a specific point in training. Runners can often describe the time or distance required for symptoms to develop. Pain resolves completely with rest, although not immediately upon stopping exercise. The diagnosis and management of CECS is discussed in detail separately. (See "Chronic exertional compartment syndrome".)

Foot and ankle injuries — Foot and ankle injuries account for up to 20 percent of running injuries and are the most common injury reported by distance runners and marathoners [30]. This is not surprising given that the ground reaction forces the foot must absorb with each stride are several times body weight. The most common foot injuries in runners are overuse injuries of soft tissues, including tendons and fascia.

Plantar fasciitis — Plantar fasciitis is the most common cause of rearfoot pain in runners. The predominant symptom of plantar fasciitis is pain in the plantar region of the foot that increases when initiating push-off while walking or running. The hallmark for diagnosis is focal point tenderness (picture 14 and figure 5). The etiology of plantar fasciitis remains unclear, but the condition is often attributed to training errors, biomechanical problems, and excessive foot pronation or supination, and it is more common in older and heavier runners [30-32]. The biomechanical abnormality most often associated with plantar fasciitis is decreased dorsiflexion of the foot and toes, and thus, stretching is an important part of treatment. Another common biomechanical problem is weakness of the plantar flexors, which some clinicians believe is best treated with eccentric strengthening exercises. The diagnosis and management of plantar fasciitis is reviewed separately. (See "Plantar fasciitis".)

Tendon injuries — Runners are susceptible to tendon injuries at a number of sites, the Achilles being most common. Others include the peroneal (fibularis), posterior tibial, and anterior tibial tendons (figure 6).

Achilles tendinopathy occurs in up to 10 percent of elite runners annually [33]; runners with more than 10 years of experience are at higher risk [34]. Among former elite male distance runners, the lifetime risk is reported to be as high as 52 percent [35]. The biomechanical factors that predispose runners to Achilles tendinopathy remain unclear but are the subject of research [36-38]. Poor flexibility of the Achilles tendon, overpronation, and valgus or varus deformity of the calcaneus all affect rearfoot mechanics, possibly increasing torque on the Achilles. Some clinicians advocate using a heel pad or orthotic in runners to counteract this effect.

Patients with Achilles tendinopathy typically complain of pain or stiffness 2 to 6 cm above the posterior calcaneus (picture 23 and figure 6). The pain is frequently described as burning, increases with activity, and is relieved by rest. Runners with the condition often have recently increased their training intensity or have been training rigorously for a long time. A history of excessive foot supination, increased speed work or hill training, or improper (eg, poorly fitting shoes, tennis instead of running shoes) or worn out footwear may be found. The diagnosis and management of Achilles tendinopathy is discussed separately. (See "Achilles tendinopathy and tendon rupture".)

Peroneal (fibularis) tendon injury may be traumatic, usually from a lateral ankle sprain, or related to overuse and associated with excessive foot pronation and weak foot plantar flexors. Examination reveals tenderness along the course of the tendon posterior or inferior to the lateral malleolus (picture 24 and picture 25), which increases with resisted ankle eversion. The diagnosis and management of non-Achilles tendinopathies are discussed separately. (See "Non-Achilles ankle tendinopathy".)

Posterior tibial tendinopathy is typically an overuse injury that develops following an abrupt increase in training intensity and is associated with poor foot and calf flexibility and excessive foot pronation. Examination findings include tenderness along the course of the posterior tibial tendon posterior or inferior to the medial malleolus, which increases with resisted inversion.

Anterior tibial tendinopathy is a common cause of anterior ankle pain in runners and often develops following abrupt increases in training, particularly hill running. Examination often reveals tenderness, and possibly swelling, of the tendon as it crosses the ankle joint. Pain increases with resisted dorsiflexion.

Overuse tendinopathy generally is reviewed in detail separately. (See "Overview of the management of overuse (persistent) tendinopathy" and "Overview of overuse (persistent) tendinopathy".)

Navicular stress fracture — Stress fractures of the tarsal navicular are more common in runners. These injuries present in a manner similar to other stress fractures and are associated with vague medial midfoot pain and focal tenderness, most often along the dorsal aspect of the navicular (picture 21). (See "Stress fractures of the tarsal (foot) navicular" and "Running injuries of the lower extremities: Risk factors and prevention".)

First metatarsal phalangeal joint — Running generates substantial forces across the forefoot and thus can aggravate hallux rigidus or hallux valgus (bunion) of the metatarsal phalangeal (MTP) joint of the great toe (ie, first MTP joint). The sesamoid bones located on the plantar surface of the MTP joint can become inflamed from running and may cause discomfort.

Hallux rigidus and hallux valgus (bunion) — There is little high-quality evidence to provide insight into the causes and guide the management of hallux rigidus. Hallux rigidus is presumed to be a degenerative condition of the first MTP joint associated with either an acute injury (eg, forced hyperextension of the great toe, so-called "turf toe") or repetitive microtrauma, as would occur with running [39,40]. Genetic predisposition may play a role. The result is limited dorsiflexion of the first MTP joint; approximately 60 degrees of dorsiflexion is needed for normal gait (picture 16). (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults", section on 'Hallux rigidus and hallux limitus'.)

Runners with hallux rigidus are typically older than 30 and complain of pain at the dorsum of the great toe. However, some runners may present with vague lateral forefoot pain. This presentation is likely due to runners shifting their body weight to the lateral foot during the foot-strike phase of running to reduce the load on the great toe. It remains unclear whether running is a cause of hallux rigidus or aggravates symptoms elicited by other factors. Shoes with a toe box that is too small or pointed may contribute.

Hallux valgus (ie, bunion) deformity is defined as a lateral deviation of the hallux (great toe) on the first metatarsal (picture 26). The etiology of hallux valgus is multifactorial and likely involves abnormal mechanics and anatomy. Patients generally complain of a deformed and painful great toe. (See "Hallux valgus deformity (bunion) in adults".)

In runners with either of these conditions, mechanically limiting first MTP joint motion by using appropriate shoes and unloading techniques can be helpful. We suggest walking shoes with a wide toe box, stiff soles, rocker bottoms, and low heels. Comfortable running shoes with a wide toe box combined with techniques to reduce the impact on the first MTP joint, such as custom orthotics or cushioned insoles, reduces symptoms in many runners. Acetaminophen or nonsteroidal antiinflammatory drugs may be used for short-term pain relief. Ice can be applied following running. Glucocorticoid injections may provide short-term pain relief for those with mild hallux rigidus [41]. Consultation with a foot surgeon should be obtained for severe or recalcitrant cases, although there is little high-quality evidence to guide decisions about surgery or conservative care.

Sesamoiditis — The sesamoids are pea-sized bones that function as pulleys for tendons (just as the patella does for the knee extensors) and assist with weightbearing. Inflammation or injury of the sesamoid bones located on the plantar surface of the first MTP joint can cause focal pain in runners, particularly sprinters (image 2 and figure 7). The runner with sesamoiditis typically complains of pain at the area of the MTP joint with weightbearing that is exacerbated by walking and even more so by running. Exquisite tenderness of the sesamoids is present and is exacerbated by dorsiflexion of the great toe. Imaging is required to differentiate between sesamoiditis and a stress fracture.

Both sesamoiditis and sesamoid stress fractures are notoriously difficult to treat and may require a short period of immobilization followed by prolonged rest from running. Runners can use alternative, nonweightbearing forms of exercise to maintain fitness. Treatment with custom orthotics, soft pads cut to relieve pressure on the sesamoids, and (in severe cases) glucocorticoid injections may be helpful, but there is little evidence to guide treatment. Female runners should avoid wearing high heels; shoes with a stiff sole (eg, clog) are often helpful. Consultation with a foot surgeon is reasonable in recalcitrant cases.

Treatment of sesamoiditis does not differ significantly from that for sesamoid fractures. The evaluation and management of sesamoid fractures are discussed separately. (See "Sesamoid fractures of the foot".)

Metatarsal stress fracture and metatarsalgia — Pain in a runner's forefoot that is not due to a metatarsal stress fracture is likely due to metatarsalgia or an interdigital (Morton) neuroma. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults", section on 'Metatarsalgia'.)

Metatarsal stress fractures typically present in a manner similar to other stress fractures and are associated with vague forefoot pain of insidious onset and focal tenderness over a particular metatarsal (image 3 and image 4). (See "Stress fractures of the metatarsal shaft".)

Metatarsalgia is a general term for pain that occurs along the ball of the foot. Most runners with metatarsalgia complain of pain in the forefoot during running; the examiner will find tenderness along the plantar surface just proximal to the metatarsal heads. The condition is often associated with overpronation and/or collapse of the transverse arch. A metatarsal pad placed proximal to the area of tenderness often relieves symptoms; in more severe cases, a custom orthotic may be needed.

Morton neuroma — Interdigital neuromas (often referred to as Morton neuroma) are thought to be due to swelling and scar tissue formation on the small interdigital nerves. They most commonly involve the third interdigital space. An intermetatarsal bursitis can cause a similar pain. Morton neuroma is reviewed in detail separately; aspects of particular importance for runners are discussed below. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults", section on 'Interdigital (Morton) neuroma'.)

The runner with a neuroma may complain of numbness of the involved toes or pain that increases with activity and is usually felt between the third and fourth toes (figure 8). Examination may reveal a clicking sensation (Mulder sign) when palpating this interspace while simultaneously squeezing the metatarsal joints. Overpronation and tight shoes are often associated with the condition.

Ultrasound offers an inexpensive option for identifying Morton neuroma with accuracy comparable to MRI and can help to distinguish a neuroma from intra-metatarsal bursal swelling or synovitis in adjacent joints.

Conservative treatment should precede expensive diagnostic procedures. This approach involves decreasing pressure on the metatarsal heads by using a metatarsal support or bar or padded shoe insert. Strength exercises for the intrinsic foot muscles are often part of conservative treatment. Treatment inserts are often placed in both shoes (even when symptoms are unilateral) to ensure that the patient walks evenly, but bilateral pads are not always needed. A broad-toed shoe that allows spreading of the metatarsal heads may be helpful. Invasive therapies may be needed should conservative measures fail. (See "Evaluation, diagnosis, and select management of common causes of forefoot pain in adults", section on 'Interdigital (Morton) neuroma'.)

Tarsal tunnel syndrome — Tarsal tunnel syndrome (TTS) is an uncommon source of foot pain in runners due to entrapment of the posterior tibial nerve or one of its branches as it courses behind the medial malleolus (figure 9). The most common causes include an acute injury and its sequelae (eg, scar tissue) or repetitive microtrauma, as occurs with running, particularly in runners who overpronate. Runners with TTS complain of numbness or burning pain, usually along the plantar surface of the foot, although complaints may be localized to the medial plantar surface of the heel, mimicking plantar fasciitis. TTS typically worsens with running or at night. Findings are almost always sensory; muscle weakness is uncommon. A positive Tinel sign may be present. As in carpal tunnel syndrome, a positive sign occurs when symptoms are elicited by tapping over the path of the nerve. TTS is discussed in detail separately. (See "Overview of lower extremity peripheral nerve syndromes", section on 'Tarsal tunnel syndrome'.)

Toenail injuries — Athletes in many sports sustain toenail injuries from repetitive trauma to the nail or nail bed. In runners, this condition is commonly called "jogger's toenail," and it most frequently affects the great toe (picture 27) [42]. The nail may turn black (due to subungual bleeding) or fall off, especially after a long-distance run such as a marathon. The differential diagnosis for these injuries includes fungal infection and subungual melanoma. The management of acute subungual hematoma, fungal infection of the nail (onychomycosis), and melanoma are reviewed separately. (See "Subungual hematoma" and "Onychomycosis: Epidemiology, clinical features, and diagnosis".)

In the author’s experience, toenail injuries in runners are most often due to poorly fitting shoes. Thus, injuries can be prevented by using properly fitted running shoes. Such shoes provide sufficient space in the toe box and are sized to accommodate the longest toe. The midfoot portion of the shoe should fit properly and be sufficiently snug to prevent the toes from slipping forward and striking against the end of the toe box.

Friction blisters — Friction blisters are caused by continual rubbing or pressure on the skin and are common among runners. They affect runners of all levels of experience, from novices to professionals, and all distances, from sprinters to ultramarathon competitors. In a study of 204 amateur runners over the age of 18, blisters were self-reported as one of the three most frequent injuries (along with sprains and abrasions) [43]. Blisters develop most often on the toes, ball of the foot, and heel (picture 28). (See "Friction blisters".)

Runners and clinicians have used various interventions to prevent blisters, with varying results reported. In our clinical experience, the following interventions are helpful:

●Wear properly fitting running shoes. (See "Running injuries of the lower extremities: Risk factors and prevention", section on 'Running shoe design'.)

●Wear properly fitting socks made from materials that reduce friction and wick moisture from the skin. Make sure the portion of the sock between the shoe and the skin is wrinkle free.

●At areas known to be susceptible to blisters ("hot spots") in particular runners, apply a viscous lubricant or a protective bandage.

For lubricants, the authors have found SkinLube and Blisterblock to be useful products. We have found Vaseline to be less effective. For protective bandages, we have found Blisterderm and Moleskin to be helpful.

Several randomized trials of paper tape for blister prevention were performed during RaceThePlanet ultramarathons (250-km [155-mile] race) in 2010 to 2011 and again in 2014. During the first trial, all 136 runner participants developed blisters during the race and reported that paper tape was not protective [44]. In a subsequent trial involving 128 race participants, the authors reported that paper tape reduced blisters by 40 percent [45]. In an observational study of ultra-distance runners, no prophylactic measures, including taping, application of talcum powder and antiperspirants, and different types of socks, reduced blister rates [46]. In this study, the only factor associated with a reduction in blisters was prior ultra-distance race experience [46]. A study from 1990 reported that acrylic fiber socks were associated with fewer and smaller blisters, but a 1993 follow-up study clarified that acrylic socks were only superior when they were knitted in such a way as to provide "anatomical padding" [47,48].

If a friction blister has formed, it should not be unroofed in most cases. However, large, fluid-filled blisters in problematic locations may be drained in sterile fashion and covered with a clean bandage. Runners generally do not need to wait until a blister has completely healed before resuming running, but it makes sense to perform alternative exercises (eg, cycling, swimming) that do not aggravate the affected area for a few days while the blister is allowed to heal. Proper technique for draining a friction blister is described separately. (See "Heel pain in the active child or skeletally immature adolescent: Overview of causes", section on 'Friction blister'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: General issues in muscle and tendon injury diagnosis and management" and "Society guideline links: Muscle and tendon injuries of the lower extremity (excluding Achilles)" and "Society guideline links: Plantar fasciitis" and "Society guideline links: Patellofemoral pain".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Achilles tendon injury (The Basics)" and "Patient education: Metatarsalgia (The Basics)" and "Patient education: Patellofemoral pain (The Basics)" and "Patient education: Iliotibial band syndrome (The Basics)" and "Patient education: Hamstring injury (The Basics)" and "Patient education: Shin splints (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Epidemiology – Up to one-half of regular runners report an injury each year. Some injuries are traumatic, but most are due to overuse and many involve the knee. The most common diagnoses include patellofemoral pain (PFP), medial tibial stress syndrome (MTSS; ie, "shin splints"), Achilles tendinopathy, iliotibial band syndrome (ITBS), plantar fasciitis, and stress fractures of the metatarsals and tibia. (See "Running injuries of the lower extremities: Risk factors and prevention", section on 'General epidemiology'.)

●Risk factors – Multiple intrinsic and extrinsic risk factors are associated with running-related lower extremity injuries. The most easily changed are training variables such as mileage and intensity. The role of other factors, such as shoes, stretching, and biomechanics, is less clear. (See "Running injuries of the lower extremities: Risk factors and prevention", section on 'Risk factors' and "Running injuries of the lower extremities: Risk factors and prevention", section on 'Training suggestions to reduce injury risk'.)

●History and physical examination – A focused history and physical examination are essential for determining the differential diagnosis and the need for diagnostic imaging. Guidance about how best to evaluate the injured runner is provided in the text. (See 'Evaluation of the injured runner' above.)

●Specific injuries – Descriptions of important and common causes of running-related lower extremity injuries, organized anatomically, are provided in the text along with links to more detailed discussions. (See 'Specific injuries' above.)

•Hip injuries (see 'Hip injuries' above)

•Knee and thigh injuries (see 'Knee and thigh injuries' above)

•Foot and ankle injuries (see 'Foot and ankle injuries' above)

•Stress fractures (see 'Stress fractures' above)

•Other conditions, including medial tibial stress syndrome (see 'Medial tibial stress syndrome (shin splints) and tibial stress fractures' above) and exertional compartment syndrome (see 'Chronic exertional compartment syndrome' above)