INTRODUCTION — Stress fractures of the tibia and fibula occur in many athletes, especially runners, and also in non-athletes who suddenly increase their activity level or have an underlying illness predisposing them to stress fractures. Many factors appear to contribute to the development of these fractures including changes in athletic training, specific anatomic traits, decreased bone density, and disease states [1].

This topic review will discuss stress fractures of the tibia and fibula in adults and children. An overview of stress fractures and discussions of other specific fractures are found separately. (See "Overview of stress fractures" and "Stress fractures of the metatarsal shaft".)

CLINICAL ANATOMY — The tibia is the major weight-bearing bone of the lower leg (picture 1 and picture 2). The proximal tibial plateau forms the lower surface of the knee joint (figure 1 and picture 3). The tibial shaft bridges the distance to the distal tibia, which contributes the superior articular surface of the ankle joint at the tibiotalar articulation as well as the medial malleolus. Another key bony landmark is the tibial tuberosity, which sits several centimeters below the knee joint line and serves as the attachment site for the patellar tendon. Although the tibial shaft is the most common site for stress fractures, they may also occur at the tibial plateau and the medial malleolus [2].

A strong fibrous structure, the interosseous membrane or ligament (figure 2), connects the tibia and fibula along the length of the two bones. Proximally, this structure, reinforced by strong anterior and posterior ligaments, forms a synovial joint, the proximal tibiofibular articulation (picture 4). Distally the interosseous membrane and three ligaments, the anterior, posterior, and transverse tibiofibular ligaments (figure 3 and figure 4), stabilize the superior ankle joint. Another fibrous structure, the crural fascia, surrounds the bones and muscles of the lower leg. Thus, although it bears far less weight than the tibia, the fibula is closely bound to the tibia by membranous and ligamentous attachments and is therefore susceptible to strain from some of the same deforming forces that cause tibial stress fractures [1].

Fascial extensions and the interosseous membrane separate the muscles, nerves, and vessels of the lower leg into four distinct compartments (figure 5): The anterior, posterior, and deep posterior compartments border the tibia; the lateral compartment borders the fibula.

Blood supply to the tibia arises from the posterior and anterior tibial arteries after they branch off the popliteal artery just posterior and distal to the fibular head (figure 6) [3,4]. The major blood supply to the tibial cortex arises from the nutrient artery, which obliquely traverses the tibial cortex entering the posterolateral tibia at the level of the soleus muscle origin. The nutrient artery has three ascending branches but only one descending branch. More limited penetration to the anterior cortex and the distal tibia likely explains in part why fracture healing in these regions can become problematic. The nutrient artery to the fibula supplies blood to fibular cortex. The peroneal artery is the largest branch off the posterior tibial artery. It descends along the lateral posterior compartment, giving off a nutrient artery to the fibula.

EPIDEMIOLOGY, RISK FACTORS, AND MECHANISM OF INJURY — Tibia and fibula stress fractures occur most commonly among athletes who participate in activities that involve prolonged walking, running, or jumping. Although most common among runners, where the incidence may be as high as 15 percent, these injuries also occur among gymnasts, ballet dancers, soccer and basketball players, and military recruits [5-9]. In a review of university athletes, three women's sports posed the greatest risk of stress fracture: cross country, gymnastics, and track and field [10]. A discussion of the risk factors for stress fractures generally is provided separately; risk factors of particular relevance to tibial and fibular stress fractures are reviewed below. (See "Overview of running injuries of the lower extremity" and "Overview of stress fractures".)

Research into the etiology of tibial and fibular stress fractures is limited; however, possible risk factors generally fall into one of three categories:

●Activity-related factors, including excessive training, poor footwear, and irregular or hard terrain [1,11].

●Biomechanical factors, including inflexibility or weakness of the calf muscles [1], unequal leg-length [12], and flat (pes planus) or high-arched (pes cavus) feet [13,14].

●Metabolic factors, including demineralized bone due to hormonal or nutritional imbalances and specific disease states.

A case control study that examined multiple variables suggests that a combination of factors may influence risk in the individuals who experience tibial stress injury [15]. The factors identified include:

●Lower muscle mass and higher body fat

●Foot anomalies, either pes planus or pes cavus

●Thinner and smaller bones, regardless of overall bone density

Increased orthotic use was also noted, but this finding is likely to be a confounder as a higher number of foot anomalies was noted in the injured group. These findings add support to prior epidemiologic studies that suggest differences in bone geometry, foot structure, and overall fitness all play some role in tibial stress fractures. The underlying features shared by this diverse group of proposed risk factors is their propensity either to increase the loading and bending forces placed on the bone or to reduce the capacity of the bone to handle such forces [11]. (See "Overview of stress fractures", section on 'Risk factors'.)

As an example, an observational study comparing 23 runners with a history of tibial stress fracture to 23 controls found that the stress fracture group had smaller bone geometry and greater bending moments in the medial-lateral axis. This would theoretically place greater bone stress on a relatively smaller bone [16]. A similar study found that the tibias of male distance runners with bone stress injuries were thinner compared with controls, particularly at mid-diaphysis, and demonstrated lower bending strength [17].

Several studies support the notion that muscle inflexibility is a significant risk factor for tibial and fibular stress fractures. A prospective cohort study of 230 high school runners followed for three years found that limited straight leg raise increased risk of tibial stress fracture in males [18]. In a study matching runners who had experienced tibial stress fractures with those who had not, researchers found reduced ankle motion during plantar flexion and greater Achilles tendon stiffness among athletes with a prior injury [19]. Additional factors such as shear strain from jumping or running activity and the ability of bone to adapt and remodel remain investigational [20,21].

Among military recruits, and to a lesser degree among athletes generally, women experience an increased incidence of stress fracture, ranging up to 3.5 times the incidence among men [11]. Although the reasons for this discrepancy remain unclear, possible causes include eating disorders, baseline fitness, endocrine factors, differences in bone density, and skeletal alignment [22]. White Americans have twice the risk of African Americans [11].

Low bone mineral density is a risk factor for all fracture types, including stress fractures. A well-controlled study looking at Marine recruits in a 32-week basic training program, matched individuals who developed a tibial stress with another healthy participant who completed the same program and was approximately the same age, height, and weight, and demonstrated comparable aerobic fitness [23]. The group with tibial stress fractures showed lower bone mineral density at the lumbar spine, femoral neck, and remainder of the skeleton. This suggests that even among apparently healthy individuals, intrinsic bone health may play a role in determining which individuals develop stress fractures.

A class of stress fractures secondary to weakened bone (ie, insufficiency fractures) occur most commonly among older women with osteoporosis, but they also affect younger amenorrheic women, patients with certain systemic diseases, such as diabetes mellitus and rheumatoid arthritis, as well as patients taking particular medications, such as long-term corticosteroid therapy. Patients with impaired nutrient absorption due to gastrointestinal disorders or bariatric surgery are also at risk. Fractures of the tibia or fibula from metastatic tumors are classified as pathologic fractures and may be mistaken for stress fractures. (See "Epidemiology and etiology of premenopausal osteoporosis" and "Overview of general medical care in nonpregnant adults with diabetes mellitus" and "Overview of the systemic and nonarticular manifestations of rheumatoid arthritis".)

Stress fractures of the tibia and fibula can occur when advanced knee osteoarthritis alters the biomechanical stresses placed on the lower extremity [24,25]. In addition, stress fractures can follow total knee arthroplasty as a complication related to alignment change or pressure from a metal stem or other components of the implant [26,27]. Similarly, the stress of an ankle arthrodesis likely increases the risk for developing a tibial or fibular stress fracture [28].

CLINICAL PRESENTATION AND EXAMINATION — Initial symptoms in most athletes with a stress fracture of the tibia or fibula may resemble medial tibial stress syndrome (MTSS), commonly referred to as "shin splints," although the time course is typically longer and the pain more focal. In most cases of lower extremity stress fracture, there is a gradual progression of activity-related pain over several weeks to possibly months [6-9,13]. Athletes often report an increase in training volume or intensity. Eventually pain worsens and may occur with rest. Occasionally, the patient experiences an abrupt increase in pain at the site of milder chronic symptoms indicating that a repeatedly stressed area of bone has finally fractured. (See "Overview of running injuries of the lower extremity", section on 'Medial tibial stress syndrome (shin splints) and tibial stress fractures'.)

Diagnosis of a tibial or fibular stress fracture is based upon a suggestive history, usually in a patient with risk factors, and the clinical findings listed immediately below (see 'Epidemiology, risk factors, and mechanism of injury' above):

●Pain that localizes to one specific area of the leg

●Local swelling and discrete bone tenderness are present

●Pain increases with the impact from running or jumping

●Positive tuning fork test is suggestive

●Positive hop test is suggestive

The tuning fork test is performed by applying a tuning fork (typically 128 Hertz) to the area of suspected injury. Although its accuracy is limited, a positive test (application of vibrating tuning fork elicits pain at the site) is suggestive of a stress fracture in the appropriate clinical setting. In a study of 55 patients whose initial plain radiographs were negative but who were suspected of having a tibial or fibular stress fracture, a tuning fork test was performed followed by a bone scan [29]. Pain on application of the tuning fork test correctly identified 53 of 67 stress fractures. According to this study, the tuning fork test demonstrated a sensitivity of 79 percent and a specificity of 63 percent. A meta-analysis of studies of clinical tests used to identify lower extremity stress fractures concluded that the tuning fork test lacked adequate sensitivity and specificity to be relied upon without further diagnostic testing [30].

An inability to hop on the symptomatic leg for 10 repetitions (positive hop test) without excessive pain suggests the presence of a stress fracture in the appropriate clinical setting. As with the tuning fork test, evidence is scant and both sensitivity and specificity are limited, reinforcing the importance of the clinical presentation and appropriate imaging studies.

A clinical prediction tool (Shin Pain Scoring System [SPSS]) to identify shin pain associated with a bone stress injury shows promise for identifying tibial stress fractures, but validation in larger prospective studies is needed [31]. The authors ask eight questions about risk, including previous fracture, amenorrhea, general health, and chronic illnesses. They follow this history with the following clinical tests:

●Tenderness to palpation

●Two-finger tap test

●Vibration sensitivity using a 128-Hz tuning fork

●Fulcrum test for tibia

●Active ankle range of motion during a weightbearing lunge

●Single-leg hop test

In a study of 80 adolescent athletes, the SPSS correctly identified the grade of just over 54 percent of tibial bone stress injuries [31].

DIAGNOSTIC IMAGING — All patients with a suspected stress fracture of the tibia or fibula are assessed initially with a plain radiograph. However, symptoms and signs precede the appearance of radiographic findings by weeks, and confirmation of the injury on the initial plain radiographs occurs in fewer than half of tibial stress fractures. Thus, particularly in the face of strong clinical suspicion, a negative plain radiograph cannot rule out such a stress fracture. Periosteal elevation, cortical thickening, sclerosis, or a true fracture line are positive findings (image 1 and image 2 and image 3). In patients whose initial radiograph is diagnostic, follow-up radiographs are not necessary unless the patient fails to improve appropriately with treatment.

In the majority of patients who do not have diagnostic initial plain radiographs, an experienced clinician may elect to treat presumptively, provided that symptoms and examination findings indicate the fracture is in a low-risk area (eg, the medial posterior aspect of the tibial shaft). High-risk sites for stress fractures are described separately (see 'Indications for orthopedic consultation or referral' below and "Overview of stress fractures", section on 'Clinical classification (grading and risk of complications)'). An important exception is an athlete or other patient who plans to embark upon a vigorous rehabilitation program; in these cases, confirmation of the fracture is required by other means, usually magnetic resonance imaging (MRI) [32].

Plain radiographs obtained three to four weeks or later following a clinical diagnosis typically show the positive findings listed above, consistent with fracture healing (image 4). However, when confirmation is required sooner, studies such as MRI, bone scan, or computed tomography (CT) are used for diagnosis. The advantages and disadvantages of the various methods for imaging suspected stress fractures are discussed in detail separately. (See "Overview of stress fractures", section on 'Imaging studies'.)

In most cases, MRI is the preferred study for the evaluation of stress fractures when a definitive diagnosis is required (image 5) [33]. With regard to tibial and fibular stress fractures, MRI may be particularly helpful because it helps to differentiate stress fracture from shin splints and demonstrates high sensitivity and specificity [33]. When an intraarticular stress fracture is suspected, MRI better differentiates bone injury from ligament or cartilage injury. Cost and lack of access to MRI may lead some clinicians to reserve its use for possible high-risk stress fractures. (See "Overview of stress fractures", section on 'Clinical classification (grading and risk of complications)'.)

Musculoskeletal ultrasound (MSK US) is a commonly used tool for fracture diagnosis in many sports medicine clinics and emergency departments (ED) [34,35]. An example of ultrasound imaging used to detect a fibular stress fracture is found in the accompanying image (image 6).In particular, emerging literature suggests that MSK US is useful for diagnosing malleoli fractures, including stress fractures (image 7 and image 8). The malleoli are superficial and easily visualized with MSK US. In three observational studies performed in the ED, MSK US showed excellent sensitivity (91 to 100 percent) and specificity (87 to 99 percent) when compared to plain radiographs or MRI [36-39]. In one such study, MSK US outperformed the Ottawa Ankle Rules in determining who needed additional radiologic imaging. (See "Ankle sprain in adults: Evaluation and diagnosis", section on 'Ottawa ankle rules'.)

Studies to determine the key MSK US findings characteristic of stress fractures in other areas of the tibia and fibula are needed. In children, characteristic changes in the appearance of MSK US images of the physis can help to identify Salter-Harris Type 1 and 2 fractures. (See 'Evaluation' below.)  

Once radiographic studies confirm the diagnosis of stress fracture, the clinician rarely needs to obtain subsequent imaging. Radiographic healing correlates only weakly with clinical healing: Both bone scan and MRI may remain positive for up to 12 months following the original injury [40]. Additional imaging plays a role only when the patient fails to improve appropriately with treatment. Studies are then performed to determine if the fracture has extended or developed an area of nonunion. In this setting, CT provides better images of the fracture line in long bones than does plain radiograph, bone scan, or MRI.

DIAGNOSIS — Stress fracture of the tibia or fibula is suspected on the basis of a suggestive clinical presentation, but definitive diagnosis is made with diagnostic imaging. The typical history is of a gradual progression of activity-related, focal leg pain over several weeks, often following an increase in training volume or intensity with athletes. Examination reveals focal bony pain, tenderness, and swelling. Initial plain radiographs may be unremarkable; ultrasound may be useful in some cases. When a definitive diagnosis is needed, magnetic resonance imaging (MRI) is highly sensitive and specific, but many cases can be managed presumptively without MRI. (See 'Clinical presentation and examination' above and 'Diagnostic imaging' above.)

DIFFERENTIAL DIAGNOSIS — The differential diagnosis for stress fractures of the shaft of the tibia or fibula includes the conditions listed below. The differential diagnosis for stress fractures of the medial malleolus and the distal fibula are reviewed separately. (See "Non-Achilles ankle tendinopathy", section on 'Differential diagnosis of medial ankle tendinopathy' and "Non-Achilles ankle tendinopathy", section on 'Differential diagnosis of lateral ankle tendinopathy'.)

●Medial tibial stress syndrome (MTSS, or "shin splints") – MTSS usually develops over a day or two, whereas symptoms from a stress fracture generally develop and increase over several weeks. MTSS causes diffuse pain along the length of the tibial shaft; there is no focal bony swelling or tenderness. Conversely, a focal, palpable area of tenderness is present in most patients with a stress fracture of the tibia. Plain radiographs are unremarkable in patients with MTSS, although this may be the case early in the course of a stress fracture. (See "Overview of running injuries of the lower extremity", section on 'Medial tibial stress syndrome (shin splints) and tibial stress fractures'.)

●Muscle strain (posterior tibialis or soleus for tibia; peroneal for fibula) – Muscle strains usually occur acutely, whereas stress fractures develop more insidiously. An important means of distinguishing these muscle strains from stress fractures is that direct palpation of the muscle elicits pain, whereas direct palpation of the tibia or fibula does not. In addition, neither percussion of the bone nor application of a tuning fork causes pain. (See "Calf injuries not involving the Achilles tendon".)

●Posterior tibialis tendinopathy – Posterior tibialis tendinopathy causes pain along the posterior medial border of the tibia, which is the most common location for a tibial stress fracture. However, resisted plantar flexion with inversion of the foot triggers more pain than direct palpation of the tibia. Peroneal tendinopathy may also mimic a fibular stress fracture, but again, pain can be elicited with resisted foot eversion and not by direct palpation of the bone. Peroneal tendons lie in a groove along the posterior border of the fibula, which is rarely a location of pain for fibular stress fractures. Ultrasound can help to distinguish tendinopathy from stress fracture. (See "Non-Achilles ankle tendinopathy", section on 'Medial ankle tendinopathy'.)

●Periostitis – Periostitis, or inflammation of the periosteum, causes symptoms similar to those of a tibial stress fracture, but swelling and tenderness are more diffuse along the posterior medial border of the tibia and do not tend to localize. Ultrasound examination may reveal diffuse hypoechoic change along the tibial border.

●Acute compartment syndrome (ACS) – ACS typically causes diffuse aching along the lower leg and a feeling of tightness and swelling within the affected muscle compartment. Pain can be severe. Unless the ACS is associated with an acute fracture, bony tenderness is absent. Stress fractures rarely cause sufficient swelling to cause ACS of the lower extremity. Should ACS be suspected, immediate assessment and surgical consultation is required, as this is a limb-threatening condition. (See "Acute compartment syndrome of the extremities".)

INDICATIONS FOR ORTHOPEDIC CONSULTATION OR REFERRAL — Primary care physicians can manage most tibial stress fractures. Stress fractures of the proximal tibia or fibula and intra-articular stress fractures of the tibia demonstrate slower healing and are best managed by either an orthopedist or a non-orthopedist with experience managing such fractures.

The most difficult tibial stress fractures to treat involve the anterior cortex, the tension-bearing side of the bone. These stress fractures are best referred to a knowledgeable orthopedist [6]. They account for approximately 5 percent of all tibial stress fractures. A linear lucency along the anterior tibia on plain radiographs, referred to as the "dreaded anterior black line," is the hallmark of this injury (image 3). Healing is often prolonged; those with markedly delayed healing (>9 months) are often treated surgically. Controversy exists as to whether surgical fixation, bone grafting, or other approaches improve outcome, and which intervention is best. Intramedullary nailing is the most common surgical intervention, but alternative approaches such as anterior tension band plating may be used [41]. While controlled trials to determine the best approach to management are lacking, multiple observational studies report that conservative care is associated with higher rates of complications and lower rates of return to sport [42]. Intraarticular stress fractures merit orthopedic consultation at a minimum.

Stress fractures of the medial malleolus are at greater risk for delayed healing and nonunion [43]. They merit close clinical monitoring to be certain healing is progressing appropriately, and they should be referred if there is evidence of delayed healing or persistent pain. A follow-up computed tomography (CT) scan may confirm nonunion when the clinical picture remains unclear.

Immediate orthopedic referral should be obtained if at any time during initial or follow-up treatment bone scan or magnetic resonance imaging (MRI) reveals a severe fracture, as determined by the appropriate radiologic grading system (see "Overview of stress fractures", section on 'Imaging studies'). Such imaging is generally obtained if symptoms are severe or patients fail to improve appropriately with conservative management.

INITIAL TREATMENT — Initial treatment consists of rest and stabilization as needed. For fractures at greater risk for delayed healing or nonunion, but which are still frequently managed by primary care physicians (eg, those of the tibial plateau and medial malleolus), treatment can include a short period of non-weight-bearing and stabilization in a long air splint, knee splint, or hinged brace. No crutches are required if the patient can ambulate in a splint with no or minimal pain. (See 'Indications for orthopedic consultation or referral' above.)

Fibular stress fractures rarely require non-weight-bearing status, with the possible exception of the rare stress fracture at the fibular head or neck that causes neuropathic symptoms from injury to the common peroneal nerve, or a high grade stress fracture that shows signs of minor displacement. Rarely is rigid immobilization necessary for tibial or fibular stress fractures unless needed for adequate pain relief.

The non-weight-bearing phase typically extends only as long as the patient experiences significant pain with walking. Once a splint allows the patient to walk with little to no pain, the patient can transition to intermittent or partial use of crutches, and then steadily to unassisted ambulation. If the patient has an intra-articular stress fracture of the tibial plateau that causes a knee effusion, a reasonable option is to continue non-weight-bearing until the effusion resolves.

The author uses whichever analgesic medication alleviates pain adequately in these patients. This may include acetaminophen and non-steroidal antiinflammatory drugs (NSAIDs). With good splinting, patients rarely require opioids and usually only short-term use of any pain medication. The effects of NSAIDs on bone and soft tissue injury healing are reviewed separately. (See "Nonselective NSAIDs: Overview of adverse effects", section on 'Possible effect on fracture healing'.)  

FOLLOW-UP CARE

Tibial stress fractures — There is no standard follow-up schedule for tibial shaft stress fractures. Follow-up is adjusted according to clinician judgment, patient symptoms, and response to treatment. Patients with injuries at relatively high-risk sites (ie, anterior tibial shaft) are seen more frequently. The author prefers to follow higher risk stress fractures every two weeks. For low-risk fractures, the first follow-up is at two weeks. For athletes who wish to return to sports quickly, two-week follow-up visits are still advisable. In individuals who are not trying to return quickly to vigorous activity, follow-up after the first visit can be monthly. For non-athletes or recreational athletes, a reasonable alternative is to cross train with stationary cycling or swimming, while using an air cast for ambulation for 8 to 12 weeks with tibial stress fractures and for six weeks with fibular stress fractures. High-risk sites for stress fractures are described separately. (See 'Indications for orthopedic consultation or referral' above and "Overview of stress fractures", section on 'Clinical classification (grading and risk of complications)'.)

A meta-analysis of studies assessing the optimal time to return to full activity following a tibial stress fracture found no conclusive evidence to make a recommendation but noted that fractures of the anterior tibia required a longer healing time and a higher proportion were treated surgically [44].

Design and implementation of an appropriate rehabilitation program is fundamental to follow-up care. Clinicians may wish to manage rehabilitation themselves, or they may refer the patient to a physical therapist. Each rehabilitation program should be constructed to meet the needs of the patient based on an assessment of the following factors [32]:

●Cause of the injury (eg, excessive or improper training, poor technique, poor nutrition)

●Nature of the injury (eg, site of fracture)

●Symptoms and examination findings

●Preinjury activity level and patient goals for treatment

●Patient age, prior injuries, and comorbidities

A relatively aggressive rehabilitation protocol allows a quicker return to sport for uncomplicated, low-risk fractures of the middle and distal third of the shaft. For these fractures, a systematic review found that treatment with a long air splint, also called a long air cast, (picture 5) enables the patient to return to activity up to six weeks sooner than standard casting and other treatments [45]. Obviously, patients with high-risk fractures, more severe symptoms, significant underlying nutritional problems or comorbidities, and/or older age must follow a much more conservative rehabilitation program to allow for complete fracture healing.

The following table outlines our basic rehabilitation program for motivated running athletes with low-risk tibial stress fractures and no complicating factors. This is a slightly aggressive program for runners who are eager to return to full activity (table 1).

Although our approach to treatment is consistent with that of many experienced clinicians who manage these injuries and with the sports medicine literature, strengthening exercises should be used cautiously during rehabilitation. Eccentric exercises and stretching may impair fracture healing, particularly if performed prematurely or too vigorously. The total time and intensity of weight-bearing must also progress gradually, so the injured bone has time to remodel and thereby increase its load-bearing capacity. Pain or persistent swelling indicates the bone requires additional rest before beginning active rehabilitation.

Throughout the course of treatment, we suggest taking additional daily calcium (1500 mg) and vitamin D (800 international units) to help ensure fracture healing. Calcium intake may be increased through dietary changes or supplementation; vitamin D intake is typically increased with oral supplements. The effect of calcium and vitamin D on stress fractures is reviewed separately. (See "Overview of stress fractures", section on 'Nutrition, bone health, and body composition' and "Overview of stress fractures", section on 'Prevention'.)

Fibular stress fractures — The treatment approach to fibular stress fractures is similar to that described above for tibial stress fractures. Most fibular stress fractures respond well to cessation of the inciting activity and can be effectively managed by primary care physicians. As most of these fractures occur in the distal third of the fibula, use of a long air splint (picture 5) similar to that used in studies of tibial stress fractures seems reasonable [46].

Most clinicians allow athletes to cross-train and use pain and limping as guidelines for when to reduce activity and when to allow resumption of regular training. For less serious fractures, brief runs on soft surfaces, while wearing an air stirrup, may be possible as early as one week after the initiation of treatment.

We approach the rehabilitation of fibular stress fractures with a protocol similar to that described above for low-risk tibial stress fractures. Training progresses in a sequential fashion so as to maintain fitness without inhibiting fracture healing. Patients are generally able to resume training three to six weeks after the initiation of treatment. A sample rehabilitation program for low-risk fibular stress fractures is provided (table 2).

However, not all fractures are amenable to this approach. Basic training for military personnel may involve activities that include repeated jumping and landing in a squat position. The authors of a study of Korean military recruits speculate that this type of biomechanical stress leads to more proximal fibular stress fractures, and these injuries heal more slowly [47]. In their study of 635 recruits undergoing six weeks of basic training, 12 fibular stress fractures were diagnosed, including 10 in the proximal third and two in the middle third.

The treatment of proximal fibular stress fractures requires a more conservative approach. The author approaches these injuries in a similar fashion to higher risk tibial stress fractures. Long air splints are used for a full six weeks. While non-weight-bearing, patients may cross train with stationary cycling or swimming. Weight-bearing is delayed until signs of clinical healing (eg, lack of tenderness, ability to jog or hop without pain or evidence of a limp) are present. Once signs of healing are evident and clinical progress appears adequate, the athlete may begin weight-bearing, generally at phase 2 of the tibial stress fracture protocol described above. (See 'Tibial stress fractures' above.)

Throughout the course of treatment, we suggest taking additional daily calcium (1500 mg) and vitamin D (800 international units) to help ensure fracture healing. Calcium intake may be increased through dietary changes or supplementation; vitamin D intake is typically increased with oral supplements. The effect of calcium and vitamin D on stress fractures is reviewed separately. (See "Overview of stress fractures", section on 'Nutrition, bone health, and body composition' and "Overview of stress fractures", section on 'Prevention'.)

Risk factor identification — Part of good follow-up care is an assessment of risk factors that may have contributed to the development of the stress fracture. Biomechanical evaluation for such things as leg length discrepancy, calf muscle inflexibility, and flat or high-arched feet should be performed. Activity-related factors such as inadequate footwear, improper running surfaces, and inappropriate training regimens should be reviewed. Metabolic factors such as amenorrhea, celiac disease, poor nutrition, and osteoporosis should be investigated where appropriate. Referral to a physical therapist or nutritionist can be helpful. Details about specific risk factors and their modification are found elsewhere. (See "Overview of running injuries of the lower extremity", section on 'Risk factors' and "Overview of stress fractures", section on 'Risk factors'.)

Consideration of the female triad (eating disorder, amenorrhea, and osteoporosis) should be given to young women with stress fractures and a concerning history. Psychiatric referral may be needed. (See "Functional hypothalamic amenorrhea: Pathophysiology and clinical manifestations" and "Eating disorders: Overview of epidemiology, clinical features, and diagnosis".)

RETURN TO WORK AND SPORTS — The protocol described above (see 'Follow-up care' above) serves as a template for the approach used in different sports. The key principle of protected, progressive exercise allows adequate bone healing while maintaining some degree of fitness, and it should be followed regardless of the sport.

Occupational demands require careful consideration. Patients with physically demanding work should likely rest until healing is nearly complete. Patients with less physically demanding jobs can often return to work with an air splint after only a week or two of treatment, while those with sedentary jobs may be able to return to work immediately.

Tibial fractures sometimes heal rapidly, and some athletes begin full training as early as eight weeks after their injury. Typically, by 12 weeks most uncomplicated fractures are sufficiently healed to allow for full training. A study of university athletes showed an average return to play period of 12 to 13 weeks for lower extremity stress fractures, including the tibia [48]. Slower progress is expected in complicated fractures, such as those of the proximal tibia, tibial plateau, anterior tibial shaft, or medial malleolus. According to a small retrospective study of military personnel, long-term outcomes for isolated tibial stress fracture appear to have little consequence in regard to full return to activity [49].

PEDIATRIC CONSIDERATIONS

Epidemiology — Pediatric overuse injuries are thought to be increasing in frequency, and this includes stress fractures of both the tibia and fibula. Most authors attribute this trend to specialization in sports at earlier ages as well as more year round training programs that involve younger athletes who are skeletally immature. The frequency of stress fracture increases with age so that only 9 percent occur at ages 15 or less, with 32 percent in 16 to 19 year olds, and 59 percent in patients over 20 [50]. While older adolescents (16 to 19 years of age) have greater bone maturity and their fracture pattern more closely resembles that of adults, stress fractures in younger children differ in presentation, location, and healing time.

Among high school athletes, the sports with the highest rate of stress fracture are girls' cross country, girls' gymnastics, and boys' cross country [51]. High school girls have almost twice the risk of stress fracture compared with boys.

Retrospective observational studies suggest that the tibia is the most commonly affected bone in children followed by the fibula [52-54]. In contrast to adults, the proximal tibia is the typical location, and midshaft anterior tibial stress fractures are rare [53].

As in adults, pediatric fibular stress fractures tend to occur distally. Proximal fibular stress fractures are uncommon and may arise from higher impact forces associated with jumping, although the precise mechanism remains unclear [8].

Approximately half of pediatric stress fractures are attributable to athletics. A significant number also occur in children with underlying osteopenia (eg, patients with congenital bone dysplasia, osteopenia from corticosteroid use and other chronic diseases associated with immobilization and weakness such as cerebral palsy), and these can evolve from sports, other recreational exercise, or normal daily activity [52].

Evaluation — Findings of pediatric stress fracture are often subtle. Children may limp with minimal pain or may have a localized area of pain with activity that on examination is sensitive to touch, percussion, or vibration. Swelling at the site or inability to ambulate is less common.

Plain radiographs of the affected area, including AP, lateral, and oblique views, are of greater diagnostic utility in children because of their rapid healing phase that promotes active new bone formation, periosteal thickening, and early callus. These findings are seen earlier and in more regions of bone than in adults. If plain radiographs are not diagnostic or are concerning for other pathology such as malignancy or osteomyelitis, then magnetic resonance imaging is the best confirmatory study.

The role of musculoskeletal ultrasound (MSK US) is expanding but evidence pertaining to its appropriate role with stress fractures in children is lacking [55]. Nevertheless, characteristic US changes around the physis, particularly when plain radiographs are unremarkable, can help to identify Salter-Harris Type 1 and 2 fractures. These finding include thickening of the perichondral ring with edema and increased Doppler flow, as well as increased fragmentation or widening compared to the unaffected extremity.

Treatment — Children with stress fractures should have limitation of activity and immobilization with pneumatic braces, lower leg appliances, or casting. Healing time averages five weeks for pediatric tibial stress fractures and four weeks for distal fibular stress fractures [52]. Orthopedic referral is indicated in the following circumstances:

●Children with anterior tibial stress fractures

●Patients who fail to respond to typical care within six to eight weeks

●Patients for whom the diagnosis of stress fracture versus other bone abnormality is unclear

Almost all children fully recover from their stress fracture with appropriate rest and immobilization.

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 fracture and stress fracture management in adults" and "Society guideline links: Lower extremity (excluding hip) and pelvic fractures in adults" and "Society guideline links: Acute pain management".)

SUMMARY AND RECOMMENDATIONS

●Tibial and fibular stress fractures occur most commonly among runners and usually result from excessive training. Most tibial and fibular stress fractures respond well to cessation of the inciting activity and can be effectively managed by primary care physicians.

●Risk factors for tibial and fibular stress fractures are of three types: activity-related, biomechanical, and metabolic. Activity-related factors include excessive training, poor footwear, and irregular terrain. Biomechanical factors include inflexibility or weakness of the calf muscles, unequal leg-length, and flat (pes planus) or high-arched (pes cavus) feet. Metabolic factors include demineralized bone due to hormonal or nutritional imbalances and specific disease states. The underlying features shared by this diverse group of proposed risk factors are their propensity either to increase the loading and bending forces placed on the bone or to reduce the capacity of the bone to handle such forces. (See 'Epidemiology, risk factors, and mechanism of injury' above.)

●Symptom onset from stress fractures of the tibia or fibula is usually insidious over weeks; pain is exacerbated by running or jumping. Athletes often report an increase in training volume or intensity. Generally, there is focal tenderness and swelling around the fracture site. Eventually pain worsens and may occur with rest. (See 'Clinical presentation and examination' above.)

●Patients with a suspected stress fracture of the tibia or fibula are assessed initially with a plain radiograph. However, symptoms and signs precede the appearance of radiographic findings by weeks. A definitive diagnosis by imaging study may not be necessary if the diagnosis is clear and clinical findings indicate the fracture is in a low-risk area (ie, not at the anterior tibial cortex). In some cases, a radiographic diagnosis is required (eg, clinical diagnosis is unclear; patient is to begin a vigorous rehabilitation program). Magnetic resonance imaging (MRI) is highly sensitive and specific. Ultrasound may be useful. Repeat plain radiographs, bone scan, and computed tomography (CT) may be used in specific scenarios. (See 'Diagnostic imaging' above.)

●Immediate orthopedic referral is necessary for stress fractures of the anterior tibial cortex and severe fractures, as determined by bone scan or MRI grading. Referral is often made for intraarticular stress fractures, including those of the medial malleolus, and stress fractures of the proximal tibia or fibula. (See 'Indications for orthopedic consultation or referral' above.)

●Initial treatment of tibial and fibular stress fractures includes rest from any inciting activity. The key principle of rehabilitation is protected, gradually progressive exercise that allows for adequate bone healing while maintaining a degree of fitness. Long air splints are recommended for immobilization during the initial weeks of healing and rehabilitation. Detailed programs for runners with low-risk injuries are provided (table 1 and table 2). Follow-up care should include assessment of risk factors that may have contributed to the development of the stress fracture. (See 'Initial treatment' above and 'Follow-up care' above.).

●Patients with physically demanding work should rest until healing is nearly complete. Patients with physically undemanding jobs can often return to work sooner while using an air splint. (See 'Return to work and sports' above.)

●Young adolescents and children with stress fractures have different patterns of injury, heal more quickly, and usually have excellent outcomes. (See 'Pediatric considerations' above.)