Scar Tissue

Scar tissue is the repair material the body lays down to close a wound once the original tissue can no longer be regenerated in place. It is built predominantly from type I collagen, laid down in dense, largely parallel bundles rather than the finer, basket-woven arrangement of undamaged skin — which is the structural reason a scar looks and feels different from the tissue around it: the fiber architecture, not just the presence of a mark, is different.

Scar tissue never fully matches the original. Mature scar collagen typically reaches only about 70–80% of unwounded skin's tensile strength, a ceiling it approaches gradually over months as the tissue remodels but does not exceed even years later. It also lacks the specialized structures the original tissue had — hair follicles, sweat glands, and normal skin architecture do not regenerate within scar tissue, which is why a scar stays permanently hairless and doesn't sweat, regardless of how faded it eventually becomes.

Scarring can also overshoot. A hypertrophic scar is raised and thickened but stays within the original wound boundary and often flattens somewhat over time. A keloid grows beyond the original wound margin entirely, invading adjacent normal tissue, and rarely regresses on its own — a distinction that matters clinically because keloids are prone to recurring even after surgical removal, while hypertrophic scars generally are not.

The same collagen-remodeling logic explains why Fracture Nonunion and problem wound healing are related failure modes at different tissue layers: bone and skin both replace damaged structure with a repair material optimized for closing the gap and restoring baseline strength, not for perfectly reconstructing what was lost.