A step-wise approach to exertional leg pain

Most family physicians are accustomed to treating active patients with shin splints and stress fractures. But many are less familiar with, and slower to recognize, other sources of exertional leg pain (ELP), defined as exercise-related pain that localizes in the lower extremity distal to the knee and proximal to the talocrural joint.¹

ELP has a broad differential diagnosis that includes other musculoskeletal conditions—most notably chronic exertional compartment syndrome (CECS), which has been found to affect 33% of athletes with chronic ELP¹—as well as a number of vascular and neurologic causes.^2-4 In addition, etiologies may overlap. Greater awareness of the many causes of ELP can help you to avoid the unnecessary use of expensive diagnostic tests as well as delayed diagnosis and treatment.

A thorough medical and activity history, symptom review, and physical examination are your most important tools when patients present with ELP. When the cause is not obvious or the patient fails to respond to conservative measures, x-rays, magnetic resonance imaging (MRI), vascular studies, electromyography and nerve conduction studies, and/or intracompartmental pressure testing may be needed to find the source of the symptoms. In the text that follows, we review both common and relatively uncommon sources of ELP, using a stepwise diagnostic approach. You’ll find a diagnostic challenge, in which you can test your skills and a more comprehensive differential diagnosis in the TABLE.^1-3,5-9

Musculoskeletal injuries: Shin splints and beyond

Medial tibial stress syndrome (MTSS), commonly known as shin splints, is characterized by pain and tenderness over the posteromedial aspect of the distal tibia.³ It typically results in diffuse pain that occurs with exercise, but may persist at rest in severe cases.^3-6 Less often, localized swelling may also be present.²

MTSS accounts for between 6% and 16% of all running injuries.^2,10 It is associated with a spectrum of tibial stress injuries, including periostitis, tendinopathy, and stress reaction, with dysfunction of the tibialis posterior, tibialis anterior, and soleus muscles thought to be contributing factors.^2,11 Intrinsic factors include high body mass index (BMI), female sex, excessive internal and external hip rotation, hyperpronation, and hyper plantar flexion.^2,10,12

X-rays of the leg are typically normal in patients with MTSS and should be considered only if the clinical presentation suggests the possibility of an alternative diagnosis, such as a stress fracture or tumor.^2-4,13 Advanced imaging such as MRI or triple phase bone scans (TPBS) are useful when the diagnosis is in question and will reveal an abnormally high signal along the posterior medial tibial surface or the classic train-track appearance of nucleotide uptake in patients with MTSS.² MRI readily shows periosteal reaction and bony edema and has a sensitivity of 78% to 89% and a specificity of 33% to 100% for the diagnosis of MTSS.^14,15

While ice, NSAIDs, proper conditioning, physical therapy, and activity modification are all appropriate treatment for shin splints, none of these interventions are more effective than rest alone.

Initial management of MTSS is conservative, with the mainstay of treatment consisting of rest, ice, and nonsteroidal anti-inflammatory drugs (NSAIDs).^3,13,16 While ice, NSAIDs, proper conditioning, physical therapy to stretch and strengthen the calf musculature, rigid orthotics to correct foot hyperpronation, and activity modification are all appropriate treatments, randomized controlled trials have shown none of these interventions to be more effective than rest alone.² Non-operative treatment is usually successful, but surgery may be required for severe or refractory cases. Procedures include posteromedial fasciotomy, release of the medial soleus fascial bridge, deep compartment fasciotomy, or removal of a section of the distal tibia periosteum.^3,4

Lower extremity stress fracture. Stress fractures are caused by repetitive loading that results in microtrauma, including bony microfractures. The vast majority of cases—80% to 95% of stress fractures—affect the lower extremities, and most involve the tibia.^2-4,6,13,17 The most common presentation is an insidious onset of pain over a specific bony area with a normal appearance, although localized swelling or erythema may occasionally be present.^3,14,17,18 The pain may be reproduced or worsened by weight-bearing activities and relieved by rest.^14,18

Consider the female athlete triad. In evaluating a patient with a stress fracture, pay close attention to dietary history, BMI, and, in female athletes, take a detailed menstrual history. Such patients are at risk for amenorrhea, low bone mineral density, and nutritional deficits—the “female athlete triad,” which carries an increased risk of stress fractures.^3,14,17-19

Stress fractures can often be diagnosed with a thorough medical history and physical, with imaging used for confirmation.^6,14,17,18 Historical features of a stress fracture that may differentiate it from MTSS include pain that is unilateral and absent at rest and occurs with more prolonged activity, as well as post-exercise and/or nocturnal pain. Notable physical exam features include pain that is reproduced in a focal area with a single leg hop or percussion with a tuning fork or ultrasound.^5,11,17

Initially, sensitivity for a plain radiograph is as low as 10%.^2,11 Abnormalities on x-ray are usually seen after 2 to 8 weeks of symptoms^2,7,11 and may include a faint periosteal reaction, a fluffy area of callus, or a cortical lucency sometimes referred to as the “dreaded black line.”^3,6,17 If a radiographic exam shows evidence of a stress fracture, further imaging is typically unnecessary. MRI or TPBS is suggested, however, when x-rays appear normal but suspicion of a stress fracture remains.^3,17,18 MRI may show edema within 3 days of symptom onset and is more sensitive and specific than computed tomography (CT) or TPBS for diagnosing stress fractures of the tibia.^2,16

Treatment of tibial stress fractures is typically non-operative and consists of alterations in activity (eg, non weight-bearing), correction of nutritional deficits, such as inadequate caloric intake or too little calcium or iron, and addressing problems with footwear, training regimen, and/or running surface.^3,14,18 Fibular and posteromedial tibial stress fractures are considered low risk and heal with weight-bearing restrictions and rest, initially for a minimum of 2 to 4 weeks.³

Posteromedial tibia injuries tend to heal well because they are on the compression side of the bone. Anterior tibia stress fractures, which are located on the tension side of the bone^2,7 and account for approximately 5% of all tibia stress fractures, are more prone to non-union or progression to a complete fracture.^7,20 Thus, anterior tibia stress injuries warrant a more aggressive approach, with treatment options including non-weight bearing status that may last longer than 8 weeks, pneumatic brace casting, and/or orthopedic referral to evaluate for surgical intervention.^7,20-22 Time for radiographic evidence of healing may exceed 8 months, so early surgical intervention should be considered, especially for high-level athletes.^7,20,21