Definition

“Shin splints” is a clinical syndrome of pain and discomfort in the anterior medial to lateral portion of the lower leg often associated with repetitive activity on hard surfaces or from forcible, excessive use of the foot flexors. The term is often used widely and variably with differing consensus of opinion as to the actual clinical syndrome and pathoanatomy. The diagnosis should be limited to musculoskeletal inflammation with an anatomical site of periostitis. It excludes stress fractures, diet-related diseases, ischemic or vascular disorders, ankle tendinopathies, ankle sprain or strains, and chronic or exertional compartment syndromes, although such diagnosis may coexist.

Shin splints most commonly occur in athletes who have sudden increases or changes in their training activity. This disorder occurs in runners and in athletes who participate in high-impact court or field sports as well as in gymnasts, cross-fit training, and ballet dancers, alone or in conjunction with other overuse syndromes. It has also been well documented and studied world-wide in military personnel. One study even suggests that while shin splints may not be the most common diagnosis in the cohort, it is responsible for 20% of all initial basic military training musculoskeletal rehabilitation resource consumption.

The etiology of shin splints is not clearly defined, but it is likely to be multifactorial, with multiple studies suggesting a myriad of biomechanical abnormalities of the foot and ankle, poor footwear and shock absorption, hard playing surfaces, and training errors. Other contributing factors may include weakness of anterior and posterior compartment musculature, inadequate warm-up, leg length discrepancy, tibial torsion, excessive femoral anteversion, and increased Q angle, as is seen in women.

One prospective study in military cadets looked at seven anatomic variables and identified greater internal and external hip range of motion (ROM) and lower mean calf girth to be associated with a higher incidence of exertional medial tibial pain in men. It also showed a high rate of injury among women, but no intrinsic factor was specifically identified. Nutritional and endocrine factors are more likely to play an etiologic role in stress reactions. In school-age athletes and adults who participate in seasonal sports, shin splints can occur when they resume their sport or start a new land-based sport (e.g., high school or college athletes who go from playing basketball to cross-country or track).

It is important for the clinician to differentiate shin splints, a fairly benign condition, from acute compartment syndrome (a potential emergency) and from the different types of stress fractures that can occur in this region. The anterior lower leg is especially predisposed to compartment syndrome because of its high vulnerability to injury and its relatively limited compartment compliance. It is most common to study these diagnoses together because many may coexist and symptoms overlap. Further discussion of these other diagnoses may be found in their respective chapters. Tibial periostitis has been described as an initial manifestation of polyarteritis nodosa. Primary adamantinoma, a rare low-grade primary bone tumor, and hydatid bone disease have also been reported in this region.

Symptoms

Patients presenting with shin splints usually complain of a dull and aching pain near the junction of the mid and distal thirds of the posteromedial or anterior tibia ( Fig. 78.1 ). Clinicians should be aware of the wide differential diagnosis of pain in this region; not all anterior tibial pains are shin splints. Symptoms are commonly bilateral, occur with exercise, and are relieved with rest. Initially the pain may ease with continued running and recur after prolonged activity. Those with more severe shin splints may have persistent pain with normal walking, with activities of daily living, or at rest.

Repetitive microtrauma and overuse in running lead to soft tissue and even bone breakdown, a process commonly called shin splints. Muscle overpull can lead to periostitis, strain, or trabecular breakdown. The area approximately 13 cm proximal to the tip of the medial malleolus along the posterior tibial cortex appears to be maximally at risk.

Physical Examination

Physical examination typically reveals generalized tenderness along the medial tibia. Mild swelling may be present. Resisted plantar flexion, toe flexion, or toe raises may aggravate symptoms, and pain-inhibitory weakness may be evident. Striking a 128-Hz tuning fork and placing it on the tibia may reproduce the pain associated with stress fractures. Patients with stress fractures will usually have point tenderness over the bone at the site of stress fracture. Lower extremity idiopathic osteonecrosis is most common in the fifth decade of life at the medial tibial plateau, whereas those with shin splints will have more widespread tenderness to palpation that is more distal than these other pathologic processes. However, longitudinal tibial stress reactions may share a common anatomic pain distribution, and one study showed tibial stress reactions in this same distal-third region.

The lower extremity examination focuses on static and dynamic components of the kinetic chain to uncover signs of coexisting lower extremity issues that may be contributing factors. These include forefoot pronation, pes cavus, pes planus, and excessive heel valgus or varus. The primary factors that appeared to put a physically active individual at risk for medial tibial stress syndrome (MTSS) were increased body mass index, increased navicular drop, greater ankle plantar-flexion ROM, and greater hip external-rotation ROM. These primary risk factors can guide health care professionals in the prevention and treatment of MTSS. Meta-analytical study confirms these factors in addition to female sex and previous running injury. Comparatively tight or weak lower extremity muscle groups should be noted for later rehabilitation goals. In particular, relative ankle plantar flexion, dorsiflexion, inversion, and eversion strength should be examined. Careful review of systems should be negative for fever, chills, night sweats, unintentional weight loss, exercise related neuropraxia, or loss of bowel or bladder control, as these may be hallmarks of more ominous underlying pathology. The neurologic portion of the examination, including sensation and muscle stretch reflexes, should be normal.

Functional Limitations

In early stages of shin splints, activity limitations occur most often during running or participation in ballistic activities. When symptoms are more severe, they may occur with walking or at rest, thus causing further functional limitations. Athletes may be unable to participate in their sport, and attempts to cross-train into other impact sports may result in worsening of symptoms. Aquatic exercise may not only be better tolerated, but therapeutic, from the standpoint of hydrostatic pressure, as well as enabling the athlete to remain conditioned from a cardiovascular standpoint and thus less likely to try and return to impact activities too early and re-injure themselves.

Diagnostic Studies

Plain radiographs are typically normal early in the disease process but may be of use in ruling out more ominous disease, especially if symptoms are manifested unilaterally. Later, there may be evidence of periosteal thickening. Radionuclide bone scanning helps differentiate shin splints from stress fracture. Diffuse radioisotopic uptake along the medial or posteromedial tibia on the delayed phase is the pattern usually seen with shin splints. A focal defined area of uptake in all phases is more consistent with a stress fracture. Fat-suppressed magnetic resonance imaging may also be useful for discrimination between stress fracture and shin splints before plain radiography shows detectable periosteal reaction. Diagnostic ultrasound has a general role in showing periosteal thickening and fluid associated with edema, and may be able to assist in confirming this largely clinical diagnosis. Exertional compartment syndrome is uncommon, but if clinical suspicion is high, compartment pressure measurements must be done to rule it out. Compartment pressure measurement has no absolute contraindications and can be performed with relative simplicity, and more recently with noninvasive pressure related-ultrasound. Avoidance of areas with overlying cellulitis is recommended. While the invasive procedure itself carries some risk of infection, this can usually be avoided with appropriate technical practices.

Magnetic resonance imaging of the lumbar spine may be indicated if lumbar radiculopathy is in the differential diagnosis or lumbar spinal stenosis is suspected in older athletes or younger athletes with a congenitally narrow spinal canal. Electrodiagnostic studies should be essentially normal, but membrane irritability manifested as positive sharp waves or fibrillations may be seen in any inflamed muscle. Nerve conductions should be normal in the absence of any concomitant nerve entrapment as may be seen in compartment syndrome conduction block would be expected in exercise-induced neuropraxia.

Differential Diagnosis

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