Overuse Injury

The pathophysiology of overuse injuries is based on the idea that tissues adapt to the stresses placed on them over time. These stresses include shear, tension, compression, impingement, vibration, and contraction. Mechanical fatigue within tendons, ligaments, neural tissue, and other soft tissues results in characteristic changes depending on their individual properties. This fatigue is theorized to initially lead to adaptations of these tissues. As the tissues attempt to adapt to the demands placed on them, they can incur injury unless they have appropriate time to heal. For overuse injuries, the rate of injury simply exceeds the rate of adaptation and healing in the tissue. Evidence also suggests that chemical mediators are involved in the initiation and propagation of overuse injuries.

Nerve tissues are at particular risk for ischemic injuries. This ischemia leads to characteristic changes in the nerve itself. The timeline generally begins with subperineurial edema, followed by thickening of the perineurium, thickening of the internal and external epineurium, thinning of the peripheral myelin, and, eventually, axonal degeneration.

One hypothesis is that the development of muscular pain originates from the nearly continuous activation of low-threshold motor units that occurs in muscles performing continuous or slow, repetitive tasks, causing depletion of adenosine 5'-triphosphate (ATP) in those fibers. With insufficient ATP, sarcoplasmic reuptake of Ca++ could be reduced, resulting in high concentrations in the cytosol, allowing Ca++ –dependent activation of phospholipase, the generation of free radicals, and damage to the muscle fibers involved. This theory has a rational physiologic basis, but it remains to be proven. Multiple studies have shown that patients with more significant work-related, upper extremity disorders exhibit more muscular activity on electromyelography (EMG) findings; however, these studies are observational and not designed to exhibit causality.

Increasing data in in vitro and in vivo human and animal models show that there are tissue-level changes associated with repetitive stress. Prostaglandin E2 has been found to be present in high quantities in overuse tissues in rat and chicken models.[5] This mediator has been suggested to influence cell proliferation, increase collagenase, and decrease collagen synthesis. Increasing loads on these tissues alters the amount of nitric oxide and prostaglandin E2. However, another hypothesis based on rat-model observations suggests that overuse may lead to an understimulation of tendon cells, rather than to overstimulation.[6]

Alterations in the regulation of genes within tendons undergoing overuse have been shown in the rat model.[7] These changes include upregulation of genes associated with cartilage, and down-regulation of genes associated with tendon. This suggests that overuse may cause a morphologic alteration of tendon tissue, causing it to become more cartilaginous.

Moderate (40 N) and high (60 N) cyclic loads are reported to create an acute neuromuscular disorder characterized by delayed hyperexcitability in the lower back. This delay is characteristic of an inflammatory state. Microtears within muscle tissue have been shown to be related to higher repetition loads and cyclic rate.[8, 9, 10, 11]

Psychosocial factors have been implicated in overuse injuries for decades.[12] A partial list includes work satisfaction, perceived physical health, perceived mental health, coping mechanisms of the patient and his/her family, perception of work-readiness, and anxiety.

A review of the English-language literature revealed specific articles focusing on ultrasonographers, equestrian athletes, ballet dancers,[13] bicyclists, baseball players, swimmers, triathletes, golfers, bull riders, martial artists, sign language interpreters, skeletally immature patients,[14] college students, heavy computer users, assembly line workers, tailors (seamstresses), surgeons, dentists, and nurses. This list dramatizes the point that at least the perception exists that many common and some uncommon ailments are associated with repetitive motion.

The Medscape Reference topic Nerve Entrapment Syndromes may also be of interest.

Frequency

United States

The incidence of overuse injuries as a whole is nearly impossible to estimate given the sheer volume of included diagnoses, as well as the difficulty in establishing clear diagnostic criteria.[15] However, several long-term, retrospective, work-related studies have estimated the annual incidence of upper extremity disorders at 4.5-12.7% per year. The frequency of injury in each diagnostic category is more appropriately left to more focused literature.

Using data from the National Athletic Treatment, Injury and Outcomes Network Surveillance Program, a study by Post et al found that in the United States, the total rate of overuse injuries for high school athletes over a period from the 2014-2015 school year to the 2018-2019 school year was 5.3/10,000 athlete-exposures (AEs). More specifically, the rate of time-loss injuries, that is, those that caused the student to be restricted from participation for a period longer than the day of injury, was 2.0/10,000 AEs, while the rate of non–time-loss injuries was 5.3/10,000 AEs. The overuse injury rate was highest for girls’ cross-country, at 19.2/10,000 AEs. The investigators also determined that greater overuse injury rates were associated with the lower extremities than with the upper extremities or the trunk and spine.[16]

A study by Roos et al indicated that compared with high school sports in the United States, the rate of overuse injuries in college sports is 3.28 times greater. The study, which used data from the National Collegiate Athletic Association Injury Surveillance System and the High School Reporting Information Online (High School RIO) sports injury surveillance system, also found that in sex-comparable sports, the rate of overuse injuries was higher in females than in males by ratios of 1.25 (college sports) and 1.55 (high school sports).[17]

In the pediatric and adolescent population, the overwhelming majority of musculoskeletal injuries related to physical activity and sport are overuse injuries.[18]  A study by Schroeder et al found that in US high school sports, the highest rates of overuse injuries were associated with girls’ track and field and girls’ field hockey.[19] (These had the second- and third-highest overuse injury rates in the above-mentioned Post study.[16] ) The study, using data from the High School RIO surveillance system, also demonstrated that 50.0% of overuse injuries resulted in less than seven days away from activity. Only 7.6% of all overuse injuries in the study resulted in greater than three weeks away from sport.[19]

Mortality/Morbidity

Overuse injuries are not associated with direct mortality. Morbidity, however, is significant. The impact of these injuries varies from the occasional annoyance to loss of function as a result of frank tissue destruction. In many performing artists, musicians, craftsmen, and workers, loss of function at even a minor level can result in a significant loss of livelihood (leading to the various difficulties associated with this loss). The direct economic impact of overuse injury in the workplace is immense. The indirect impact is nearly incalculable if the number of health care dollars involved is considered. Of particular note, one interesting review of worker demographic data suggested that workers with cumulative trauma disorders were subjected to employment discrimination. Depression and quality-of-life issues have been described after a diagnosis of chronic overuse injury.

Race

Race is not a differentiating factor for overuse injury incidence.

Sex

For a variety of hypothesized reasons, differences in sex play a role in certain overuse injuries.[20] Most notably, researchers found a significant female predominance in carpal tunnel syndrome. This has a variety of possible causes, including anatomical differences in the carpal tunnel, hormonal differences, and, importantly, differences in the activities performed by men and woman. Other biomechanical differences have also been implicated; elbow carrying angles, Q-angles, femoral anteversion, and lean body mass are the most commonly stated. Psychosocial and cultural phenomena also play roles.

The aforementioned study by Post et al found that in high school athletics, girls’ sports had a higher total overuse injury rate (7.7/10,000 AEs) than did boys’ sports (4.1/10,000 AEs).[16]

Age

Age would be expected to be an independent risk factor for overuse injury; however, given the dependence of overuse injury on activity and the changes in activity that typify aging, the contribution of age as a risk factor is difficult to determine.[21]

The first and most crucial step is obtaining comprehensive information on the onset, timing, and frequency of symptoms; any associated symptoms; and alleviating and exacerbating factors. More detailed information about the culprit activity or technique problem is also key. Systemic symptoms should be elicited, if present. Other hallmark symptoms may include a history of popping, clicking, rubbing, erythema, or vascular phenomena.[2] When interviewing an athlete, specific attention must be paid to training details, equipment fit, and technique.

The examination should begin with the basics of inspection, palpation, and passive and active range of motion (ROM). Tenderness and guarding are often present. Crepitus, either painful or painless, is often found during the ROM examination. Obvious erythema, swelling, and anatomic derangement raise the possibility of an acute injury or infection, as well as the presence of an inflammatory disease.[22] For physical findings associated with specific injuries, refer to the specific articles in the Differentials section.

The most important factor leading to overuse injury is repetitive activity, although the specific type of force leads to different outcomes.[23]

One group of authors accurately described the issue as "a culprit and a victim," in which the victim is the injured tissue, and the culprit is the true biomechanical cause. All too frequently, physicians focus on the victim tissue and not on the culprit.

Repetition is part of the definition of overuse injury. The concept is that overuse injury is associated with repeated challenge without sufficient recovery time.

Cycles and fundamental cycles are terms used to describe activities repeated at work. A cycle is a large-scale activity that is repeated throughout the day. A fundamental cycle is a small component of a cycle that may be repeated several times during the performance of a cycle. If a job has cycles that are repeated many times a day, the job is designated as repetitive. The tendency in industry to specialize labor for the sake of efficiency and better productivity has resulted in fewer different tasks per job. These tasks are repeated frequently, and this repetition is believed to be a contributing factor to the increase of overuse injury claims. Repetitiveness and force exerted are features of a task that increase the risk of sustaining an overuse injury.

However, there have been studies that dispute this theory, finding that cycle times and repetitive motions do not specifically lead to overuse injury in the upper extremity. Most articles in the literature, though, implicate repetitive motions as possible causes of injury,

Vibration, especially over long periods, has long been shown to be a factor in increasing the risk of many injuries (eg, lower back pain, intervertebral disk injury, wrist injury). One systematic review estimated that workers with hand-arm vibration exposure had a 4-5 times greater likelihood of developing neurologic and vascular diseases (ie, carpal tunnel syndrome, Raynaud phenomenon).[24]

The greater the forces involved in an activity, the greater the chance of developing an overuse injury.[25]

Malpositioning limbs away from their neutral position increases the risk for overuse injury. Multiple articles in dental and surgical literature emphasize this point. Ergonomics is the field that focuses primarily on designing devices that lend themselves to good positioning. A massive increase has occurred in the amount of ergonomically designed work equipment, especially keyboards and mouses. The literature remains divided on their effectiveness in decreasing injuries.

A literature review found a moderate association between hand-arm symptoms and increasing duration of mouse use.[26, 27] There was a weaker association between neck-arm symptoms and mouse use. Nevertheless, prolonged computer and mouse use does not typically result in chronic neck and shoulder pain.[28] However, certain psychosocial factors may be predictive of chronic pain.

A literature review by Arnold et al concerning skeletally immature athletes with overuse physeal injuries found that risk factors for such trauma include periods of accelerated growth, body size, previous injury, chronologic age, and training volume.[14]

A prospective study by Jayanthi et al indicated that child athletes with a high degree of sports specialization are more likely to suffer injury, including overuse injury, than are less specialized athletes. The investigators, who looked at athletes aged 7-18 years, reported this outcome to be more likely in females. The study also found that those young athletes for whom the number of hours spent training each week exceeds their age are at greater risk for overuse injuries, as are those who spend more than twice as many hours per week in organized sports than in free play.[29]

A study by De Bleecker et al indicated that in athletes competing in sports that require repeated use of landing maneuvers, knee overuse injuries are more likely in those whose landing is characterized, at initial contact, by greater hip adduction and increased knee internal rotation, as well as by greater peak knee external rotation and reduced ankle dorsiflexion at peak vertical ground reaction force. Moreover, overuse injuries of the groin were found to correlate with greater range of motion in the pelvic and hip frontal and transversal planes.[30]

Laboratory tests are rarely contributory to the evaluation of overuse injury, and no laboratory results contribute to the diagnosis of overuse injury. However, several tests are generally ordered during the initial workup to rule out other etiologies of pain, depending on the patient's presentation, including, but not limited to, the following:

• Erythrocyte sedimentation rate

• Rapid plasma reagent testing

• Antinuclear antibody testing

• C-reactive protein

• Complete blood count (CBC)

• B12

• Thyroid-stimulating hormone (TSH)

• Comprehensive metabolic panel (CMP)

The diagnosis of most overuse injuries does not require imaging studies. However, if surgical intervention is considered, imaging studies are vital for the decision-making process.

Radiography

Bony avulsions are relatively common among people who participate in dance, athletic activity, and heavy physical labor. Radiography is useful for defining these bony avulsions.

Stress fractures; calcification of tendons, which occurs in persons with chronic tendonitis; joint mice; myositis ossificans; heterotopic ossification; and atrophy of cartilage generally are revealed with radiography.

Bone scanning

This may reveal stress fractures that are not evident on radiographs.

Magnetic resonance imaging (MRI)

Typically, MRI is more effective for acute injuries; findings are generally more subtle with chronic injuries.

MRI is increasingly effective for revealing the site of nerve compression when large nerves are involved (eg, ulnar, median, sciatic), but it is not yet definitive for smaller nerves. Its true sensitivity is still being determined for these uses.

MRI has been quite successful in revealing tendon, ligament, and muscle injuries. It is easily available, does not involve radiation, and can help to assess chronicity of soft-tissue injuries.

The presence of bone marrow edema on MRI scans may precede visualization of stress fractures of the cortical bone and indicates trauma to the trabecular portions of the bone.

Banks and colleagues published a review of MRI findings in athletes' overuse injuries.[31]

Ultrasonography

In the hands of a skilled clinician, US can be a quick and effective method in the clinic to assess for fluid collections, impingements, and/or soft tissue tears associated with many overuse injuries. However, US typically is not utilized as much in the surgical planning process as the aforementioned imaging modalities.

Electrodiagnostic testing (eg, EMG, nerve conduction studies) can be very useful when employed in the appropriate scenarios. In cases of peripheral nerve compression or injury, such testing can provide evidence of the location and severity of the injury. EMG and nerve conduction studies are not tests with high specificity, although they can provide much-needed information when vague symptoms are the chief complaint. They are also very useful for documenting work-related injuries.

Physical Therapy

Relative rest, particularly avoidance of the inciting activity, is a hallmark component of treatment. Using the involved area in nonpainful ways often helps to maintain ROM. Total bed rest is virtually never advisable for these patients. Participation in a carefully planned physical therapy program is important for the following reasons:

• Patient education

• Supervised use of the injured part[32]

• Appropriate use of modalities (eg, transcutaneous electrical nerve stimulation units, similar electrical treatments, ultrasound/phonophoresis, iontophoresis, heat/cold)

• Development of a home exercise program

• Psychosocial benefits related to frequent interaction with an active partner in the treatment regimen

In a randomized clinical trial, the short- and long-term effect of an exercise training program used for treating adductor-related groin pain in athletes was evaluated. The program had 47 participants who agreed to be interviewed and examined in an 8- to 12-year follow-up. The results found that the exercise program had a long-lasting effect on the participants and is the first time an exercise treatment program for overuse injuries to the musculoskeletal system has had this significant of an outcome.[33]

The physical therapy program also offers the patient the chance to see that movement will not lead to ongoing tissue damage, thus preventing significant "sick behaviors" or kinesophobia.

Overuse injury in athletes is commonly caused by ill-fitting equipment (eg, in cycling), overtraining/overreaching (eg, with regard to triathlons, marathons, etc), or technique flaws.[34, 35] Specialized bike-fitting is available, sports psychology is worthwhile in combating overtraining, and sport-specific coaching is often invaluable. Coaches, athletes, and physicians must work together to correct these problems and maintain a healthy musculoskeletal system.

See also the following related Medscape topic:

Medical Interventions Effectively Treat Overuse Injuries in Adult Endurance Athletes

Occupational Therapy

Occupational therapists with experience in this field can help to identify workplace modifications. In cases of individuals with disabilities who develop overuse injuries as a result of the interface with adaptive equipment, occupational therapy may be of great benefit. Often, simple modifications in the manner in which the patient performs activities of daily living or modifications in the equipment itself confer relief.

Vocational rehabilitation and work-hardening programs are often effective for bringing motivated patients back into the workforce. Integration of this type of program has proven to be effective in the corporate world and has decreased the overall financial impact of overuse injuries in the workplace.

Steroid injections are the most commonly used procedure in the treatment of overuse injuries, although controversy surrounding this treatment is still readily apparent. Tendons and ligaments can become structurally weakened by the use of steroids, predisposing them to rupture. The use of local anesthetics and steroids should be reserved for patients with significant pain who have the ability to change the underlying cause behind their injury. Repeatedly injecting patients who will inevitably return to the same routine that initially caused the injury is not advisable[4]

Many steroid injections can be performed under ultrasonographic guidance to increase accuracy and decrease the possibility of intratendon or intraligament injection.

Significant medical complications are quite rare with conservative treatment of these disorders. Adverse drug reactions and side effects occur, but they usually resolve with cessation of the medication. Comorbidities, such as diabetes, may be exacerbated by medications, particularly injections of steroids, which may yield elevations in blood glucose levels. Injections and surgical procedures may be accompanied by bleeding or infection. Insufficient treatment can result in chronic pain and disability, depression, and/or insomnia. These complications may require additional, more complex treatment.

Surgical intervention is undertaken if conservative approaches fail and if the injury is amenable to surgery. Decompression of nerves and repair of lax or failed ligaments are the most common overuse injuries that lead to surgery. Surgeries that are performed solely to relieve pain in the absence of objective findings are notorious for suboptimal outcomes.

Overuse injuries in athletes are often most effectively treated by a physician with experience in sports medicine and a thorough knowledge of the kinetic chain.[36] Patients with injuries stemming from the performing arts are also often best served by a physician who deals extensively with that population. Consultation with an orthopedist or neurosurgeon is appropriate if conservative measures are unsuccessful.

According to the aforementioned study by Arnold et al, overuse physeal injuries in young athletes can be prevented by limitations in participation and via sport-specific training programs. Once an overuse physeal injury has occurred, the best treatment was found to be an extended interval of active rest and, when necessary, immobilization of the joint.[14]

A meta-analysis looking at prevention strategies for lower extremity overuse injuries in runners showed that there is poor evidence at this point for a generalized approach to prevention that is suited to the majority of athletes. Currently, prevention strategies should be tailored to the individual and his/her specific risk factors (ie, work type, anatomy, biomechanics).[37]  

Nonsteroidal anti-inflammatory drugs (NSAIDs) are mainstays in the conservative treatment of overuse injuries. However, considerable evidence has been revealed that true inflammation is rarely a component of these disorders, especially tendinopathies. Consequently, the use of simple analgesics has become more prevalent in the treatment of such disorders.

Muscle relaxants, opiates, corticosteroids, tricyclic antidepressants, and sleep medications have a role in the tailored treatment of individuals with overuse injury.

Injection of involved structures with combinations of corticosteroids and local anesthetics is frequently quite helpful in persons with overuse injuries. Pain relief enables more effective participation in therapy, and it may help to limit the likelihood that the patient will develop a chronic pain syndrome. In most cases, injections should be performed after less invasive measures fail. Rarely, immediate relief of pain may be necessary to allow participation in an athletic or performing arts event, and this can be achieved through injection therapy. Techniques for the injection of specific structures are described in more specific articles in the Medscape Reference Journal (eg, see the related Medscape Drugs & Diseases topic Corticosteroid Injections of Joints and Soft Tissues).

The related Medscape Drugs & Diseases topic Chronic Pain Syndrome may also be of interest.

Class Summary

Most commonly used for relief of mild to moderate pain. Effects in treatment of pain tend to be patient-specific.

Diclofenac (Voltaren, Cataflam)

Used to reduce inflammation; inhibits prostaglandin synthesis by decreasing activity of COX enzyme, which, in turn, decreases formation of prostaglandin precursors.

Class Summary

Thought to work centrally by suppressing conduction in the vestibular cerebellar pathways. May have an inhibitory effect on the parasympathetic nervous system.

Cyclobenzaprine (Flexeril)

Acts centrally and reduces motor activity of tonic somatic origins, influencing alpha and gamma motor neurons. Structurally related to TCAs. Skeletal muscle relaxants have modest, short-term benefit as adjunctive therapy for nociceptive pain associated with muscle strains and, used intermittently, for diffuse and certain regional chronic pain syndromes. Long-term improvement over placebo has not been established. Often produces a "hangover" effect, which can be minimized by taking the nighttime dose 2-3 h before going to sleep.

Class Summary

Pain control is essential to quality patient care. It ensures patient comfort, promotes pulmonary toilet, and enables physical therapy regimens. Many analgesics have sedating properties, which are beneficial for patients who have sustained injuries.

Hydrocodone and acetaminophen (Vicodin, Vicodin ES, Lorcet-HD, Norcet, Lortab)

Drug combination indicated for moderate to severe pain.

Class Summary

Used in the treatment of overuse injury, not for their antidepressant effects but as adjunct pain medications. Act synergistically with narcotic analgesics and appear to alter brainstem pain processing. Their sedating effects also may be used advantageously if the patient's sleep is disrupted.

Amitriptyline (Elavil)

Analgesic for certain chronic and neuropathic pain.

Class Summary

Sleep-inducing medications are used in overuse injury when the patient's sleep is disrupted because of discomfort from the injury.

Trazodone (Desyrel, Desyrel Dividose, Oleptro)

Inhibits serotonin reuptake by antagonizing 5-HT2A/C, which can decrease onset time to sleep and improve slow-wave sleep.

Zolpidem (Ambien)

Structurally dissimilar to benzodiazepine but similar in activity, with the exception of having reduced effects on skeletal muscle and seizure threshold.

Class Summary

Have anti-inflammatory properties and cause profound and varied metabolic effects. Used for pain relief and reduction of inflammation.

Cortisone (Cortone)

Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.

Minimizing repetition when possible, optimizing techniques within the offending activity, minimizing vibration and force, and avoiding awkward positioning are the first steps in prevention.

Improving job satisfaction, as well as teaching stress management techniques and coping skills, has led to some decrease in repetitive stress injuries.

Athletes may require an expert evaluation of their techniques in order to determine any modifications that can be used. Proper-fitting equipment is also crucial in preventing overuse injury. Foot orthoses can reduce the injury rate in the lower limbs.[38]

Most overuse injuries resolve after 3-6 months. However, unless the offending causes are addressed, recurrences are quite common. Patient motivation and commitment to prevention are key to rehabilitating these injuries.

Home exercise programs tailored to the individual's biomechanics are another important facet of treatment.

Recovery after surgery varies depending on the procedure.

Education is an indispensable part of the treatment program for patients with overuse injuries. For several reasons, the interested patient should receive as detailed an explanation of the diagnosis and the treatment program as possible.

• Conveying this information establishes patient confidence that the physician is knowledgeable and trustworthy. Without this confidence, the patient is likely to seek help elsewhere or may not adhere to the recommended treatment program.

• Patients also should agree with the physician's explanation of the problem so that they will participate appropriately in the intervention program. If a patient does not believe in an allopathic explanation of his/her disorder, the patient is unlikely to participate effectively in an allopathic treatment program

• Education also gives patients reasonable expectations of the interventions planned and of their own responsibility to follow recommendations at home (eg, activity modification, exercise).

The causes and prevention of overuse injuries must be explicated, and it is appropriate to state that this is an area of some controversy within the medical community. For individuals such as athletes and performing artists who are highly motivated to resume the offending activity as soon as possible, emphasis must be placed on the long-term consequences of returning to their activities too early. For those with probable secondary-gain issues, the physical and psychological complications of lack of activity must be emphasized.

For patient education resources, see the First Aid and Injuries Center. Also, see the patient education articles Repetitive Motion Injuries and Sprains and Strains.