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A standard approach to describing the body and its conditions is essential for communication among healthcare providers and insurers. Use of standardized terminology is increasingly important with the expanded use of electronic medical records that follow the patient among providers. The use of standardized language improves the validity and reliability of outcome measures and interpreting evidence as it applies to the diagnosis and management of the pathology.

Interestingly, even terminology changes as more and more is known about the body. For example, until recently "tendinitis" was used to describe most nonacute tendon pathologies. We now know that many tendon conditions are not inflammatory in nature, as the "itis" suffix implies. Instead, tendon pathology often results from degenerative changes, and the term "tendinosis" is more appropriate. It is easy to see how the nomenclature might influence the treatment. A patient with an "itis" might effectively be treated with agents designed to reduce inflammation. Treatment of a patient with an "osis" would likely take a different path. In addition to a common labeling approach, a common understanding of how different tissues respond to different types of stress is critical to understanding how various mechanisms result in injury.

Tissue Response to Stress

The tissues that form the human body react to the forces—stress—placed on them in a meaningful and predictable manner, as described by the Physical Stress Theory (Fig. 4-1).1 The term "stress" is broad and encompassing enough to describe physical forces applied to the body as well as psychological, social, and emotional factors. This chapter focuses on the physical forces applied to human tissues, but one should recognize that social stresses are an important factor in determining the patient's level of disability. Emotional stresses will affect both the patient's reaction to the injury and also the perception of pain. In addition, stress can affect the body systemically, such as cardiovascular and muscular enhancements when running, or regionally, such as when performing a one-armed biceps curl.


Physical Stress Theory. The body and specific tissues respond in a predictable manner to stresses placed upon them.

Some stress is needed for soft tissue and bone to maintain homeostasis (maintenance level). This level of activity varies from person to person, but, as long as the stressors applied to the body stay within this range, no physiological changes occur. When the relative level of applied stress falls below the maintenance level, the tissues atrophy. This can be seen after long-term immobilization of an arm or leg: when the cast or brace is removed, the girth of the muscles of the immobilized portion of the limb is significantly less than the healthy limb.

Hypertrophy occurs when the duration and magnitude of the stress applied to the body are progressively increased at a rate ...

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