Physiology of Inflammation

Stages of Inflammation:

Acute and chronic are terms commonly used to refer to the duration or the length of the problem, giving inaccurate information about the actual stage of inflammation. 

 For clarity of treatment, we need to define healing by the stage of inflammation and the symptoms, not the duration of the problem.

The three stages of inflammation:

  1. Acute -swelling stage

  2. Subacute – regenerative stage

  3. Chronic – scar tissue maturation and remodeling stage

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Acute Inflammation is the swelling stage.  During this stage there is inflammation, redness and swelling due to the vascular changes.  There is exudation of cells and chemicals that cause the swelling and the pain.  If there is bleeding, hematomas form in this stage.  Secondarily, the chemical irritants are neutralized, the area is sealed off from surrounding tissue and circulation is impaired.  there is early fibroblastic cell activity. Symptoms are pain at rest and aggravated by activity.  the pain is felt over a diffuse area.  Secondary muscle spasm and guarding restrict passive movement.  In ROM, pain is felt before the tissue resistance is felt.  With injury to very deep structures or poorly vascularized areas, surface swelling and edema may not be noticeable. 

The subacute stage is the time of healing and repair.  Noxious chemicals are further neutralized. New capillary beds growing into the damaged areas are supported by connective tissue growth (collagen fibers) and together form granulation buds.  This new tissue is fragile and must be handled gently as it is easily injured.  Visible signs of inflammation subside.  ROM increases with pain felt at the point of tissue resistance.

The Chronic Inflammatory stage is the remodeling stage.  Signs of inflammation are absent and scar tissue is maturing. Pain is felt in the ROM after the tissue resistance at the end feel.  Maturation refers to the growth of the fibroblasts to fibrocytes and remodeling refers to the organization of and shrinking of collagen fibers along lines of stress.

In order to determine if the condition of the injury is in the acute, subacute or chronic inflammatory stage an adequate case history is needed along with assessment.  The history should include all incidence leading to the condition, past injuries and activities and a description of the symptoms being experienced.  The assessment should include a visual scan, active muscle testing, passive range of motion testing and resisted isometric muscle tests and palpation of the structure involved.

Treatment in acute stages includes intervention for the inflammation: ice, compression, elevation, relaxation and drainage.  Sports massage techniques use only gentle applications with no direct application of compression to the site of swelling.  Lymphatic drainage and relaxation of the muscle spasm are the acute treatment focus.  Avoid massaging the site of acute inflammation for the first 24 hours (unless you have been trained in this).  Activities should be limited to avoid unnecessary work of an injured part.  Too much use can re-injure the tissue.  However, a normal level of function and movement needs to be maintained to encourage proper tissue modeling and repair. 

A prolonged chronic stage or persistent disorder is not healing properly.  This may be caused by abnormal modeling of tissue during resolution of an acute disorder or injury.  Without resolution, abnormal amounts of collagen are produced, forming crosslinks that adhere to adjoining structures.  This limits the extensibility of the structure as well as prevents the formation of a smooth gliding surface between adjoining structures.  Proper amounts of mobilization are required for normal healing and prevention of adhesions.

Immature scar tissue is susceptible to re-tearing during repeated use.  Mobilization too early in the rehabilitation program can interfere with healing if the tissue is re-injured before it is properly healed.  Lack of adequate mobilization can result in adhesions that tear the injured tissue once movement is introduced.  The goals of treatment have not been met, inflammation has not been resolved and exercise to maintain normal use has not been incorporated.

Comparison of Stages of Inflammation

Stages of Inflammation Time Frame Symptoms ROM & Pain
Acute – beginning of healing stage From the moment of injury up to 3-4 days post injury Redness, Swelling (edema), heat, pain and often loss of function.  Muscle spasm and guarding.  Bruising if present, is black, blue, red or purple Pain is secondary to muscle spasm and guarding
Early Subacute – Granulation tissue and epithelialization stage. Within two days to two weeks Affected area shows diminishing signs of inflammation, pink, warm, slightly edematous, somewhat less painful tissue.  Muscle spasm diminishes.  Bruising if present, relatively unchanged With ROM pain is experienced when tissue resistance is encountered.
Late Subacute – wound retraction and scar remodeling stage Begins 2nd to 3rd week of subacute stage May or may not be a pocket of residual swelling.  Minimal discomfort but potential loss or ROM due to adhesions and muscle weakness.  If bruising present it changes to yellow, brown, green and then disappears. Pain is encountered with overpressure (stretch) to the affected tissue
Chronic- restoration of function Overlaps with the latter part of the subacute stage at about 2-3 weeks post injury up to 1-2 years Inflammatory process is resolved.  No edema, but there is loss of full ROM Pain is encountered with overpressure (stretch) to the affected tissue or secondary stress placed on the contracture

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