AUTHOR AND EDITOR INFORMATION

Section 1 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Background

Overuse injuries, otherwise known as cumulative trauma disorders, are described as tissue damage that results from repetitive demand over the course of time. The term refers to a vast array of diagnoses, including occupational, recreational, and habitual activities.

Pathophysiology

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. 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 shows 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.¹ 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.²

Alterations in the regulation of genes within tendons undergoing overuse have been shown in the rat model.³ 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.^{4, 5, 6, 7}
 
Psychosocial factors have been implicated in overuse injuries for decades.⁸ 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, bicyclists, baseball players, swimmers, triathletes, golfers, bull riders, martial artists, sign language interpreters, skeletally immature patients, 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.

See also the following related eMedicine topic:
Nerve Entrapment Syndromes

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.⁹ 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.

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.¹⁰ Most notably, a significant female predominance in carpal tunnel syndrome has been noted. 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. 

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.

CLINICAL

Section 3 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

History

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.¹¹  When interviewing an athlete, specific attention must be paid to training details, equipment fit, and technique.

Physical

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, 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. For physical findings associated with specific injuries, refer to the specific article in Differentials.

Causes

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

• 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, studies have been performed 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 tend to implicate these repetitive motions as possible causes for 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).
• The greater the forces involved, the greater the likelihood of developing an overuse injury.
• 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.¹² 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.¹³ However, certain psychosocial factors may be predictive of chronic pain.

DIFFERENTIALS

Section 4 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Other Problems to Be Considered

Acromioclavicular degeneration (eg, Acromioclavicular Joint Injury)
Ankle degeneration
Anterior cruciate laxity (eg, Anterior Cruciate Ligament Injury)
Elbow degeneration (eg, Elbow and Forearm Overuse Injuries)
Knee degeneration
Neck pain
Pronator teres syndrome
Shin splints
Suprascapular nerve compression
Tibialis anterior tendinopathy
Tibialis posterior tendinopathy
Achilles tendinopathy

See also the following related Medscape topic:
Tendinopathy -- From Basic Science to Treatment

WORKUP

Section 5 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Lab Studies

• Laboratory tests are rarely contributory to the evaluation of overuse injury. No laboratory results contribute to the diagnosis of overuse injury, although several tests are generally ordered during the initial workup to rule out other etiologies of pain, depending on the patient's presentation.
• • 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, and liver function tests are also used for initial evaluation.

Imaging Studies

• 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 most 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.¹⁴

Other Tests

• Electrodiagnostic testing (eg, EMG, nerve conduction studies) can be very useful when used appropriately. 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.

Procedures

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

TREATMENT

Section 6 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Rehabilitation Program

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 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 part¹⁵
• 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

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/over-reaching (eg, with regard to triathlons, marathons, etc.), or technique flaws.^{16, 17} 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.

Medical Issues/Complications

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 may result in chronic pain and disability, depression, and insomnia. These complications may require additional, more complex treatment.

Surgical Intervention

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

Consultations

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. 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.

MEDICATION

Section 7 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Injection of involved structures with combinations of corticosteroids and local anesthetics frequently is quite helpful in persons with overuse injury. 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 eMedicine Journal (eg, see the related eMedicine topic Corticosteroid Injections of Joints and Soft Tissues).

Nonsteroidal anti-inflammatory drugs (NSAIDs) are mainstays in the 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.

See also the following related eMedicine topic:
Chronic Pain Syndrome

Drug Category: Corticosteroids

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

Drug Category: Nonsteroidal anti-inflammatory drugs

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

Drug Category: Muscle relaxants

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

Drug Category: Narcotic analgesics

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.

Drug Category: Tricyclic antidepressants

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.

Drug Category: Anxiolytic agents

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

FOLLOW-UP

Section 8 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Deterrence/Prevention

• 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.

Prognosis

• 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.

Patient Education

• 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 athletes and performing artists, who generally are people 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 excellent patient education resources, visit eMedicine's Sports Injury Center and Muscle Disorders Center. Also, see eMedicine's patient education articles Repetitive Motion Injuries and Sprains and Strains.

MISCELLANEOUS

Section 9 of 10  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• In what can be called a litigious era in medicine, all interactions with patients should be undertaken with an awareness of possible future legal involvement. This awareness further compels clinicians to be accurate, thorough, and reasonable in the presence of the patient and with any documentation. Assuming the physician is knowledgeable and reasonable, an amiable doctor-patient relationship is the best way to prevent being sued. The clinician's notes may be part of a workers' compensation chart, which frequently is subject to legal review. A physician may be deposed as the treating physician or as an expert witness. In any of these situations, appropriate documentation is very desirable.
• Legal concerns are quite rare when only conservative interventions are prescribed. Poor outcomes from invasive procedures are far more likely to prompt a lawsuit. Be sure to perform injections and other procedures in a manner consistent with community standards and for clear reasons. The patient's fully informed consent is crucial.

See also the following related Medscape topic:
Resource Center Medical Malpractice and Legal Issues

Special Concerns

• The experience of Australia in the 1980s regarding repetition strain injury raises awareness of the potential for abuse in this field.^{18, 19} Repetition strain injury was briefly noted to be a rapidly increasing problem in the late 1970s and early 1980s among telephone operators and bank employees; in some settings, there was a 1-year increase in incidence of as much as 275%.
• • Reviews of this public health phenomenon have concluded that no pathologic findings, no examination findings, and no consistently abnormal laboratory findings were apparent.
  • Although the patients who reported upper extremity symptoms worked in a range of different jobs, young to middle-aged female employees in low-paying, monotonous jobs with low prestige complained most commonly.^{20, 21} Avoidance of work did not result in improvement in many cases; instead, steady deterioration of subjective symptoms was often observed.
  • Although controversial, repetition strain injury has been called a psychosomatic symptom complex and an iatrogenic epidemic of simulated injury.
  • The frequency of complaints of repetition strain injury dropped dramatically, although less rapidly than the complaints had arisen, when the Supreme Court of Australia made a landmark decision against a plaintiff alleging repetition strain injury; educational efforts were undertaken by those who recognized the pattern of abuse. Similar historic precedents have been recorded in which the removal of the secondary gain has resulted in a decline in reported complaints of these injuries.
• Repetition strain injury is distinguished from commonly accepted overuse and degenerative conditions by the presence of the following:
• • Clearly defined and distinguishable subjective symptoms
  • Recognizable gross and microscopic pathologic features
  • Reproducible, objective clinical findings
  • Appropriate responses to effective forms for physical therapy or treatment

REFERENCES

Section 10 of 10

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• References

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Article Last Updated: Mar 12, 2008