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Myofascial Pain in Athletes: Differential Diagnoses & Workup

Author: Auri Bruno-Petrina, MD, PhD, Clinical Trainee, Pemberton Marine Medical Clinic, N Vancouver
Contributor Information and Disclosures

Updated: Feb 8, 2008

Differential Diagnoses

Ankle Impingement Syndrome
Iliotibial Band Syndrome

Other Problems to Be Considered

Fibromyalgia is fundamentally a different condition than TrPs, but it often presents with symptoms that are confusingly similar to those caused by chronic MTrPs. Fibromyalgia is characterized by a central augmentation of nociception that causes generalized deep tissue tenderness that includes muscles. It has a different etiology than MTrPs, but many of the tender points diagnostic of fibromyalgia also are common sites for TrPs and many patients have both conditions. In the German literature, fibromyalgia usually is equated with generalized tendomyopathy (generalizierte tendomyopathie).

The term fibrositis appeared in the English literature in 1904 and was soon adopted into German literature as the fibrositis syndrome. For most of the century, most authors characterized fibrositis as a tender palpable fibrositic nodule. Many of these patients had TrPs. In time, fibrositis became an increasingly controversial diagnosis because of multiple definitions and no satisfactory histopathological basis for the nodule. The diagnosis was completely redefined in 1977, and the condition described by the 1977 definition was officially established in 1990 as fibromyalgia. According to the current definition of fibromyalgia, it is a totally different condition that is unrelated to the original concept of fibrositis. Fibrositis is currently an outmoded diagnosis.

By 1921 the term muskelharten was well recognized in German literature and still appears in German occasionally but rarely in English. It literally means muscle indurations and refers to the palpable firmness of the tender nodule responsible for the patient's pain. Another German term, myogelosen (literally muscle gellings) refers to the same phenomena, and the 2 terms have frequently been used interchangeably. The term muskelharten is often used to characterize the physical findings, and the term myogelosen is used to identify the diagnosis.

This term myofascial pain syndrome has acquired both a general and a specific meaning. The 2 meanings need to be distinguished. The general meaning includes a regional muscle pain syndrome of any soft tissue origin that is associated with muscle tenderness and is commonly used in this sense by dentists. The other meaning is specifically a myofascial pain syndrome caused by TrPs. This is a focal hyperirritability in muscle that can strongly modulate central nervous system functions.

The term myofascitis is now rarely (and should not be) used as synonymous with MTrPs. Myofascitis is properly used to identify inflamed muscles.

The term myogeloses is the English form of a German term, myogelosen, which is still commonly used and is generally considered synonymous with muskelharten. The name myogeloses was based on an outmoded hypothesis to account for muscle contraction that was proposed before the actin-myosin contractile mechanism was discovered. A recent study indicates that myogeloses and TrPs identify the same condition approached from somewhat different diagnostic points of view by using different terminology.

Nonarticular rheumatism is a commonly used, but not very clearly defined, general term for soft tissue pain syndromes that are not associated with a specific joint dysfunction or disease. The term generally is considered as synonymous with soft tissue rheumatism, which is the English translation for the German term weichteilrheumatismus.

Weichteilrheumatismus was commonly used to describe a range of conditions that also include myofascial pain caused by TrPs. Currently, the term nonarticular rheumatism is used to identify muscle pain syndromes that are not fibromyalgia and are not attributed to MTrPs. The literature reviews of nonarticular rheumatism by Romano include conditions such as adhesive capsulitis, periarticular arthritis, bursitis, epicondylitis, insertion tendinosis, and tennis elbow, which are frequently MTrPs masquerading as another diagnosis.

The term osteochondrosis is used by Russian vertebroneurologists as an inclusive term to cover the interaction of neural and muscular conditions, such as fibromyalgia, MTrPs, and spinal nerve compromise.

The term soft tissue rheumatism usually is used synonymously with nonarticular rheumatism.

Tendomyopathy is the English version of the German term that is divided into general and local categories. General tendomyopathy is considered synonymous with fibromyalgia. The localized form often includes MTrPs but is not as clearly defined.

Overuse syndrome

In contrast to postexercise muscle pain, overuse muscle pain often occurs in well-trained muscles. Overuse pain arises from the repetitive use of a muscle, not from a single bout of exercise. These injuries are most common in athletes, musicians, and factory-line workers, where precise repetition of motor tasks is frequently a requirement for success.

The cause of overuse muscle pain is thought to be microtrauma that outpaces the capacity of the muscle for repair. Edwards describes the final common pathway of muscle pain beginning with an excessive force per muscle fiber, leading to hypoxia, acidosis, and metabolic depletion, followed by calcium-mediated cellular damage. In laborers, continued use of fatigued muscles causes mechanical damage that is directly related to the heaviness of the work. Again, eccentric work seems to subject small numbers of muscle fibers to excessive loads.

Many occupations require precise manipulations, leading to excessive contraction of the proximal stabilizers that is unrelated to the heaviness of the task. The forces required to perform the task are not large enough to overload the muscles and cause damage. Rather, the conflict of motor control between the postural stabilizers and the muscles needed for precise manipulation or movement leads to the fiber damage.

The combination of mental stress and precise manipulations experienced by musicians/athletes can lead to occupational cramps believed to be of central origin (focal dystonia). These cramps may be just an extreme example of the muscle pain that can occur with disordered motor planning. They occur more commonly early in the career of the performer, before the smooth, seemingly effortless motor patterns are established.

Age

When children with musculoskeletal pain complaints were examined for MTrPs, the TrPs were found to be a common source of their pain. It gives the impression that the likelihood of developing pain-producing active TrPs increases with age into the most active, middle years. As activity becomes less strenuous in later years, individuals are more likely to be aware of the stiffness and restricted motion resulting from latent TrPs.

Workup

Laboratory Studies

• No laboratory test or imaging technique is generally established as useful in the diagnosis of TrPs
  • Three measurable phenomena help to objectively substantiate the presence of characteristic TrP phenomena, and all 3 are valuable as research tools.
  • Two of them, surface EMG and ultrasonography also have much potential for clinical application in the diagnosis and treatment of TrPs.

Imaging Studies

• In addition to EMG recording, ultrasonography provides a second way of substantiating and studying the LTR and it also has a strong potential for providing a much needed available imaging technique that could be widely used to objectively substantiate the clinical diagnosis of TrPs.
• This test would require the examiner to use the skill-demanding snapping palpation technique, or to insert a needle into the TrP, to elicit the twitch response.

Other Tests

• Surface electromyography
  • TrPs cause distortion or disruption of normal muscle function.
    • Functionally, the muscle with the TrP evidences a 3-fold problem: It exhibits increased responsiveness, delayed relaxation, and increased fatigability. Together, these effects increase muscle overload and reduce its work tolerance. In addition, the TrP can produce referred spasm and referred inhibition in other muscles.
    • With the recent appearance of online computer analysis of EMG amplitude and mean power spectral frequency, a few pioneer investigators have reported the effects of TrPs on muscle activity. The reports indicate that TrPs can influence the motor function of the muscle in which they occur and that their influence can be transmitted through the central nervous system to other muscles.
    • To date, the number of well-controlled studies to establish the clinical reliability and application of these observations is insufficient, but findings from the few reports of these TrP effects are promising.
  • The strong clinical effects of TrPs on sensation, as evidenced by TrP tenderness and referred pain, are well documented.
    • Strong cutaneous stimuli (eg, electric shocks) are well known to cause reflex motor effects (eg, flexion reflex). If the skin can modulate motor activity and if TrPs can modulate sensory activity, the fact that TrPs can also strongly affect motor activity should not be surprising. In fact, the motor effects of lips may be the most important influence they exert, because the motor dysfunction they produce may result in overload of other muscles and spread the TrP problem from muscle to muscle.
    • Accumulating evidence now indicates that the muscles targeted for referred spasm from TrPs also usually have TrPs themselves. These motor phenomena of TrPs deserve serious competent research investigation.
  • An increased responsiveness of some affected muscles is indicated by abnormally high amplitude of EMG activity when the muscle is voluntarily contracted and loaded. Clinical evidence suggests that some muscles tend to be shortened and abnormally excitable, while others appear to be weak and inhibited.
  • Fatigability noted at EMG and in terms of work tolerance, of the trapezius muscle that had MTrPs is accelerated compared to a contralateral muscle that was pain-free. The EMG amplitude increased and median power frequency decreased significantly in the involved muscle compared to the uninvolved muscle. Both of these changes are characteristic of initial fatigue.
  • Median power frequency generally is accepted as a valid criterion of muscle fatigue. Delayed recovery following fatiguing exercise commonly is seen in patients with muscle-related cumulative trauma disorder (CTD). MTrPs were very common in the involved muscles in this group.
  • Delayed relaxation is commonly seen in muscle-overload work situations. This failure to relax is a common surface EMG finding during repetitive exercises of muscles with MTrPs.
  • In addition, the TrP can induce motor activity (eg, referred spasm) in other muscles.
• Algometry
  • Sensitivity to pain in patients with TrPs can be measured as the pain threshold to electrical stimulation or applied pressure. The use of pressure algometry is most commonly reported.
  • Pressure algometry involves the induction of a specific pain level in response to a measured force perpendicularly applied to the skin. The following 3 endpoints are reported: (1) onset of local pain (ie, pressure pain threshold), (2) onset of referred pain (ie, referred pain threshold), and (3) intolerable pressure (ie, pain tolerance).
  • Most commonly, the pressure required to reach pain threshold is directly measured on a spring scale that is calibrated in kilograms, newtons, or rounds. Because the pressure is applied through a circular footplate, its diameter is a factor, and the actual measurement is stress (in kilograms per square centimeter) applied to skin.
  • For example, one of the most common algometers has a footplate area of 1 cm²; therefore, its meter, which provides readings in kilograms, is numerically the same as the number of kilograms per square centimeter, and no numeric conversion is needed.
• Thermography
  • Thermograms can be recorded by using infrared radiometry or films of liquid crystal. Recording infrared radiation (ie, electronic thermography) with computer analysis provides a powerful tool for tile accurate rapid visualization of skin temperature changes over large areas of the body. This technique can demonstrate cutaneous reflex phenomena characteristic of MTrPs. The less expensive contact sheets of liquid crystal have limitations that make reliable interpretation of the findings considerably more difficult.
  • Each of these thermographic techniques is used to measure the skin surface temperature to a depth of only a few millimeters. The temperature changes correspond to changes in the circulation within, but not beneath, the skin. The endogenous cause of these temperature changes is usually sympathetic nervous system activity. Therefore, thermographic changes in skin temperature are comparable in meaning to changes in skin resistance or changes in sweat production. However, electronic infrared thermography is superior to these other two measures (ie, infrared radiometry or with films of liquid crystal) in convenience and in spatial as well as temporal resolution.
  • In summary, Fisher's research studies indicate that the finding a hot spot on the thermogram is not sufficient to identify a TrP beneath it. A similar temperature change can be expected in radiculopathy, articular dysfunction, enthesopathy, or local subcutaneous inflammation. The thermographic hot spot of a TrP is described as a discoid region 5 to 1 (3 cm in diameter, displaced slightly from directly over the TrP).

Procedures

• Procedures to confirm diagnosis of MPS: The first international symposium on myofascial pain and fibromyalgia was held in 1989. It marked one of the first meetings of the principal proponents of the 2 major muscle pain syndromes. In the proceedings of that symposium, Simons listed the clinical criteria for diagnosis of MPS.
• Clinical criteria for the diagnosis of MPS caused by active TrPs
  • To make the clinical diagnosis of MPS, the findings should include 5 major criteria and at least 1 of 3 minor criteria. The 5 major criteria include the following:
    • Regional pain complaint
    • Pain complaint or altered sensation in the expected distribution of referred pain from a MTrP
    • Taut band palpable in an accessible muscle
    • Exquisite spot tenderness at 1 point along the length of the taut band
    • Some degree of restricted range of motion, when measurable
  • The 3 minor criteria include the following:
    • Reproduction of clinical pain complaint, or altered sensation, by pressure on the tender spot
    • Elicitations of a local twitch response by transverse snapping palpation at the tender spot or by needle insertion into the tender spot in the taut band
    • Pain alleviated by elongating (stretching) the muscle or by injecting the tender spot (TrP)
  • Additional symptoms, such as weather sensitivity, sleep disturbance, and depression, often are present, but they are not diagnostic because they may be attributable to chronic, severe pain perpetuated by multiple mechanical and/or systemic perpetuating factors.
• The required features include regional pain, referred pain, or disturbed sensation in a predicted location; a taut band; a tender point along the taut band; and restricted range of motion.
• One of 3 of the following minor criteria also must be present:
  • Pain complaint reproduced by pressure on the tender spot
  • A local twitch response
  • Relief of the pain by stretching or injecting
• At the same time, Simons listed research criteria for the identification of TrPs. To qualify, the point must be exquisitely tender, located in a taut band of a muscle with restricted range of motion, refer pain when pressed or needled, and exhibit a twitch response when needled.

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