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Blunt force injuries — abrasion, contusion and laceration
Blunt force produces three types of wound — abrasion of the upper skin layers, contusion (bruise) from torn vessels under intact skin, and laceration where the skin tears from crushing or stretching — and each tells something different about the object, the direction and the force.
Why it matters in the exam
Questions turn on distinguishing laceration from incision and on what can and cannot be concluded from an injury. A laceration is recognised by irregular, crushed margins, tissue bridges (nerves, vessels and fibres) stretched across the wound and intact hair within it; on the scalp over bone a laceration can look straight and clean like an incision, and the tissue bridges decide. An abrasion shows direction — scraped skin heaps up on the side towards which the body or object moved — and sometimes copies the object's pattern, such as a sole or a tyre.
A bruise can be patterned: a rod or stick produces two parallel stripes with a pale centre (tramline), a pinch produces two small oval marks facing each other, and a firm grip produces round fingertip-sized bruises. A bruise is not always at the site of the blow: blood tracks with gravity, for example from a blow to the forehead to around the eyes. Ageing a bruise by colour is unreliable; yellow only suggests it is not very fresh, and no precise age should be given from appearance. Children, older adults and patients on anticoagulants bruise more easily.
Defence injuries are bruises and abrasions on the backs of the forearms, the hands and the outer arms, produced when a victim raises the arms to protect the head. Injuries in several planes, on the inner arms and on the ears raise suspicion of assault rather than a fall. Some bruises become more visible after death as the skin pales, so more bruises may be found at autopsy than were recorded in life.
Key points
- Three types: abrasion, contusion and laceration.
- Laceration: irregular margins and tissue bridges.
- A patterned bruise shows the object: tramline, pinch, fingertips.
- Ageing a bruise by colour is unreliable.
- Defence injuries on the forearms and hands point to assault.
Summary table
| Type | Appearance | What it shows | Pitfall |
|---|---|---|---|
| Abrasion | Epidermis removed, heaped edges | Direction of movement, pattern of object | Reading a postmortem abrasion as injury in life |
| Contusion | Blood under intact skin | Shape of object (tramline, pinch, fingertips) | Ageing it by colour |
| Laceration | Irregular margins, tissue bridges | Crushing or stretching force, usually over bone | Confusing it with an incision on the scalp |
| Defence injuries | Backs of forearms, hands | Assault with resistance | Attributing them to a fall |
A free exam question
אדם החליק ברחוב והחלק העורפי של ראשו נחבל במדרכה. הוא הובהל לבית החולים ובבדיקת ה CT נראו בין השאר קונטוזיות באונות המצחיות דו צדדית. בעורף נמצאו חבורה ושפשוף. הוא אושפז להשגחה ובהמשך השתחרר. לאחר מספר ימים הופיעו חום, צמרמורות והקאות. הוא אושפז ועלה חשד למנינגיטיס מה ה מקור אפשרי למחולל ה מנניגיטיס במקרה זה?. (the question as examined, in Hebrew)
- א. הדבקה נוזוקמיאלית מעירויים במהלך האשפוז
- ב. תהליך של נמק באזור של הקונטוזיות
- ג. שבר ב cribiform plate .במהלך הנפילה
- ד. שבר אוקסיפיטלי
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Sources
- Knight's Forensic Pathology, 4th edition (2016) — The pathology of wounds — blunt injuries
- Saukko P, Knight B. Forensic Pathology (as above) and Simpson's Forensic Medicine, 14th edition (2020) — Injury assessment and interpretation
- Payne-James J et al. Encyclopedia of Forensic and Legal Medicine, 2nd edition (2016) — Bruises and their ageing
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.