Basics of Tissue Healing

There are 3 phases of tissue healing that are inter-related and overlap with one another:

Phase I: Inflammatory (Acute)

• Lasts 24-48 hours, completely over by 2 weeks 
• 5 cardinal signs of : 
• Redness 
• Swelling 
• Pain 
• Heat 
• Loss of function
• Initial vasoconstriction to limit blood loss with release of serotonin 
• Followed by histamine release which increases permeability of capillaries, so fluid escapes 
• Also released are bradykinin, other proteins and enzymes which generally increase pain so individual protects part from further injury 
• White cells move in to remove debris via phagocytosis 
• Minimizing the release of debris (protein, enzymes) from the damaged cells and minimizing hemorrhage decreases the size and amount of injury, even after the fact 

Phase II: Proliferation or Repair (Subacute)

• Lasts 4-21 days 
• Increased tissue tolerance, yet still fragile 
• Synthesis, orientation, and deposition of new collagen is random 
• Characterized by: muscle tightness, weakness, local edema, resolving pain (hopefully) 
• Rapid proliferation of collagen with fibroblastic activity

Phase III: Remodeling (Chronic) 

• Day 9- onward 
• Steady increase in scar matrix 
• Collagen fibers begin to align themselves with the prevailing tissue stresses 
• Tissue gradually assumes the appearance & function of the “host” tissue 
• Scar tissue is rarely as strong, mobile or vascular as the host 
• If new tissues are immobilized for prolonged periods, new collagen becomes highly disorganized and random