An atrophic scar looks sunken and has a pitted appearance. These scars happen because underlying structures supporting the skin, such as fat or muscle, are lost. This type of scarring is often seen in acne, chickenpox, other diseases (especially Staphylococcus infection), surgery, certain insect and spider bites, or accidents. Atrophic scars can also be common in genetic connective tissue disorders, such as Ehlers-Danlos syndrome.
Linear scars can be divided in two groups:
i) Hypertrophic linear scars which are red, raised and sometimes itchy; they are confined to the borders of the original injury. These scars develop within weeks of surgery and may worsen for three to six months before improving. These scars when mature (the process of scar maturation/healing is complete) may be raised, slightly rope-like in appearance and wide. Full maturation can take up to two years.
ii) Stretched linear scars appear when the fine lines of a surgical scar become stretched and widened. These scars are typically flat, pale, soft, symptomless scars and are common after knee or shoulder surgery. Scars that healed with some wound infection or have had stitches that dehisced (burst open) also may be wide, but these scars tend to become hypertrophic. Stretch marks after pregnancy are variants of stretched scars. Unlike hypertrophic scars they are not raised or thickened, and they tend to be smooth rather than bumpy.
A small keloid is a focused raised, often itchy scar that extends over the normal surrounding skin. It may develop years after the injury and doesn’t improve without treatment. Surgical excision is often followed by recurrence (re-appearance of the keloid), particularly if surgery is not done with other treatments such as radiotherapy.
Scar hypertrophy is caused by an overproduction of collagen during pathological (non-normal) wound healing. Scar tissue usually becomes thicker than the surrounding healthy skin during the first months, this normally reduces over time. Increased scar thickness is often called hypertrophy. Burn scars frequently remain hypertrophic to some extent, but scar atrophy (the scar being lower than the surrounding skin) also can happen in some scar.
Cutaneous scars are required to glide and stretch with healthy skin for normal physiologic function, especially near joints. However, scars are generally stiffer than normal skin. This is mainly because the scar is thicker and has an inferior collagen quality. Pliability is a term used to represent the reduced extensibility of the collagen fiber network and the amount of mechanical tension in the scar. This stiffness may cause limited joint mobility, pain and a sensation of ‘stuckness’ or ‘stiffness’ in the tissues.