Why Wound Tension Is One of the Most Important Factors in Scar Outcome

Two people can have the same operation, performed by the same surgeon, closed with the same technique, and end up with visibly different scars. Some of that difference comes from intrinsic factors such as genetics, skin type and age, and some from extrinsic factors such as how the wound was closed and how it healed. A substantial part of it is mechanical. The tension acting across a wound while it heals is a significant influence on the scar that eventually forms and, unlike many other factors, it can potentially be influenced.

This is why a scar across the shoulder often behaves differently from one on the scalp or the shin, and why a scar that looked perfectly acceptable at three months can be wide and pale at eighteen.

When skin is cut, the edges naturally pull apart. That does not mean the wound is opening. Skin normally sits under a degree of resting tension, which varies considerably depending on where it is on the body and what lies beneath it.

Sutures hold the wound edges together against that resting tension, but they do not remove it. The tension continues to act on the healing tissue during the weeks and months in which the scar is forming. It is also affected by movement — every time an underlying muscle contracts, a joint moves or the skin stretches during normal activity.

A scar over the sternum is therefore under tension from the resting state of the skin, from every breath, and from movement of the chest, shoulders and arms. A scar on the scalp, by contrast, sits over a relatively fixed surface with much less movement and mechanical strain.

Mechanical tension does more than simply pull a scar wider. It can also influence the cells involved in healing.

Fibroblasts are the cells responsible for producing collagen during wound healing, and they respond to mechanical tension. Under sustained load, they can produce more collagen and become more contractile. Some develop into myofibroblasts, specialised cells that help draw the wound edges together.

In normal healing, myofibroblasts do their work and gradually disappear as the scar matures. When mechanical loading persists, this process can be prolonged, contributing to continued collagen production and contraction of the scar.

Persistent mechanical tension can also contribute to ongoing inflammation. Inflammation and fibrosis are closely linked, and prolonged inflammatory activity is associated with excessive and more disorganised collagen formation. These processes are relevant to hypertrophic scars, keloids and scar contractures [1].

Problematic scarring is more common in some areas of the body than others, and mechanical tension is one reason why.

The anterior chest and shoulders are among the higher-risk sites. Both are under resting tension and are repeatedly loaded by breathing and upper limb movement. The upper back, jawline, neck and upper arms can also be exposed to considerable movement and tension.

Research examining how skin stretches and contracts at different anatomical sites has shown that pathological scarring is more common in areas exposed to greater mechanical forces [2].

The suprapubic region is another highly mobile area. This is where caesarean and abdominoplasty incisions are usually placed, which has direct implications for how these scars heal and are managed.

The effects of a scar are not always limited to the scar itself. This is particularly important when a scar crosses or sits close to a joint.

For example, a tight scar across the front of the shoulder can affect shoulder movement and alter the way the neck, the arm, and trunk move to compensate. Patients may therefore experience tightness, discomfort or restriction some distance from the scar itself.

This relationship is sometimes described in terms of the kinetic chain — the way movement and mechanical forces are transferred through connected parts of the body. Dr Andrea Issler-Fisher has published a review in Burns examining how the biomechanics of movement and these kinetic chains influence both the development and the treatment of scars, with illustrative cases [3]. Understanding a scar within that wider pattern of movement can be important when assessing and treating scars that restrict function.

Where and how an incision is made can influence the eventual scar, and this starts before the operation begins.

Skin has natural lines of tension, often referred to as relaxed skin tension lines. Where possible, placing an incision in a favourable direction relative to these lines can reduce the tension acting across the wound and may reduce the likelihood of widening or thickening.

This is not always possible. Access, safety and oncological clearance take priority, and some incisions simply have to be placed where the underlying problem is.

How the wound is closed also matters. Ideally, much of the tension is supported by the deeper tissue layers rather than the skin sutures alone. Without adequate deeper support, tension may be transferred to the healing scar after the sutures are removed. This is one reason a scar can look very fine at two weeks and gradually widen over the following months.

Yes, and this is a common reason people seek assessment.

Scar tissue continues to remodel for a year or more after injury. During this time it remains mechanically weaker than normal skin. A scar exposed to ongoing tension can therefore gradually stretch even if the wound originally healed without complication. Patients often describe a scar that was “fine at first” and then slowly spread.

Activity during the early postoperative period can contribute to this. Restrictions on lifting, stretching and exercise are intended, in part, to reduce excessive loading while the scar is still immature. Returning to strenuous activity too early may increase the risk of scar widening.

This distinction matters because the two behave differently and are treated differently.

A widened or stretched scar is usually flat or slightly depressed, often pale, and simply broader than the original incision.

A hypertrophic scar is raised above the skin surface and may be red, firm or itchy. It contains excess scar tissue but remains within the boundaries of the original wound. A keloid, by comparison, extends beyond the original wound boundary.

Tension can contribute to both, but treatment differs. A hypertrophic scar may respond to treatments aimed at reducing excess scar tissue and improving its characteristics, including laser, intralesional treatment, compression and silicone.

A widened scar does not have excess scar tissue to reduce. Where improvement is appropriate, surgical revision may be considered: removing the widened segment, re-closing the wound with appropriate deeper support and then managing tension during healing.

Once healing is established, several approaches can help manage the mechanical environment around a scar.

Taping and silicone. Paper tape or silicone tape may help reduce strain across a healing scar. Silicone also maintains hydration of the outer skin layer, which can influence scar maturation. Consistent use over time is generally more useful than intermittent application.

Compression. Sustained pressure remains an important part of scar management, particularly for larger or raised scars. Custom garments, pressure clips and moulds can influence scar maturation and help reduce scar thickness.

Physiotherapy and scar mobilisation. Controlled, graded stretching and scar mobilisation can help maintain tissue length, improve movement between tissue layers and preserve range of motion around joints. The aim is to maintain length in the surrounding tissue rather than to stretch the scar itself, since sustained stretch across a scar can contribute to widening.

This is different from the persistent, uncontrolled mechanical tension that can contribute to fibrosis. Therapeutic movement is deliberate and graded according to the stage of healing.

Where a scar is adherent to deeper tissues, mobilisation may help improve glide between tissue planes. Where a contracture is developing across a joint, therapy is often an important part of treatment and is generally most useful when integrated with other scar-management strategies.

Activity modification. Following postoperative restrictions is also part of tension management. Limiting certain movements or activities while a wound is vulnerable can reduce unnecessary mechanical loading during early healing.

If you have previously developed widened, raised or keloid scars, it is worth mentioning this before surgery. A history of problematic scarring may influence how the incision and postoperative scar management are planned.

Useful questions can include where the incision will sit, how the deeper layers will be closed, what activity restrictions apply and for how long, and whether early scar management may be appropriate.

Assessment may be worth considering if a scar is:

• widening or spreading
• becoming progressively raised or firm
• remaining persistently red
• becoming tight or restricting movement
• causing ongoing pain or itch.

Reviewing a problematic scar while it is still actively remodelling may allow treatment to be considered before the scar has fully matured and stabilised.

Scarless – The Clinic assesses widened, stretched and tension-related scars, including established surgical scars, in Sydney.

All procedures carry risks and potential complications. A comprehensive consultation and clinical assessment are required to determine suitability. Individual results may vary.