A pressure sore is any redness or break in the skin caused by too much pressure on your skin for too long a period of time. The pressure prevents blood from getting to your skin so the skin dies. Normally the nerves send messages of pain or feelings of discomfort to your brain to let you know that you need to change position, but damage to your spinal cord keeps these messages from reaching your brain. You may need to learn new ways to change your position to prevent too much pressure. Pressure sores can occur, for example, when you sit or lie in one position too long.
Shearing is also a kind of pressure injury.
It happens when the skin moves one way and the bone underneath it moves another way. An example of this is if you slouch when you sit. Another type of injury, an abrasion, can occur when pulling yourself across a surface instead of lifting. This is an example of a friction injury. In addition, short exposure to high pressure, such as a bump or fall, may cause damage to the skin which may not show up right away.