Pressure Ulcers, pressure sores or bed sore causes

A pressure sore, or decubitus ulcer is caused mainly by the restriction of blood flow and/or lymphatic drainage as a result of excessive tissue deformation caused by by constant pressure or friction (shear forces).

Other names for this condition include bed sores, pressure ulcers and decubitus ulcers ('lying down' ulcers).

The skin over bony areas, such as the heels, elbows, the back of the head and the tailbone (coccyx), are particularly at risk.

Pressure Ulcers can be difficult to treat.


Factors that contribute to pressure ulcer include:


Heavy pressure blocks or occludes blood vessels. The greater the pressure the less time it takes to block. The smaller the area, the greater the pressure, hence bony areas are more prone to pressure sores.

Shear forces (friction):

Skin being pulled sideways over muscle or bone when moving can stretch and block the blood vessels, restricting blood flow to skin. Excessive shearing can affect deeper tissues. Necrosis (tissue death) can occur from inside and move out. Abrasion or friction causes the surface of the skin to be rubbed away faster than it can be replaced.

Temperature and moisture of skin:

Excessive heat and moisture can contribute to the development of pressure sores. These factors can increase the vulnerability of tissues to damage from pressure and shear forces.


Areas are more subject to pressure sores

Pressure ulcers are usually found on the bony prominences. The majority are fund on the large bony areas in the pelvic region of the body.

These include the ischial tuberosity, sacrum, coccyx, trochanter, and iliac crest.
They may also form on the heels, ankles and knees.

Sitting pressure points

Sacrum, Ischial Tuberosity, Heels.

Wheelchair pressure points

Scapula, Elbow, Sacrum & Coccyx, Ischial Tuberosity, Heels, Plantar Surface of foot.

Side Lying pressure points

The malleolus, condyles, trochanter, ribs and ear are at risk from pressure when side lying.

Supine pressure points

Decubitus ulcers occur at sites overlying bony structures that are prominent when the person is lying down. The location of the pressure ulcer will depend on the person's position and the length of time he/she remains in that position. The bony prominences that support weight in the supine position are the occiput (back of the head), scapula, sacrum and heels.

Decubitus ulcers may occur on the scalp, back, tailbone, hip, heel, or any other area to which pressure is applied while a person is lying down.


People at risk of pressure ulcers, pressure sores or bed sores & pressure related problems:

  • Paraplegics/quadriplegics, Frail elderly, Wheelchair users
  • Sciatica - back pain, decreased sitting intolerance, Weight loss/chronically ill
  • Surgery - decreased sitting tolerance

The aims of a pressure care product are:

  • Increase the area of support and therefore distribute and decrease the pressure
  • Re-distribute weight and pressure away from bony prominences (bony points)
  • Control temperature and moisture

Points to consider when selecting a pressure care product:

  • The age, weight and height of a person
  • Nature and degree of disability, physical capabilities and strength
  • Lifestyle - activity and mobility, Duration of sitting or lying each day
  • Balance and posture, Skin sensation, Pressure sore history - condition of skin
  • Continence of person, Attitude and motivation to take responsibility for skin care.

Body Part Definitions

Sacrum: The sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx (tailbone).

Ischial tuberosities: The sitting bones in the bottom or butt.

Coccyx: Contains 4 small fused bones known as the tail bone.

Trochanter: The greater trochanter is the name given to bony protusion at the top of the femur.

Iliac crest: Hip bone.

Scapula: Shoulder blade.

Malleolus: The lateral malleolus is the bony bit on the outside of the ankle and the medial malleolus is the bony bit on the inside of the ankle.

Condyles: femoral condyle is the end of the thigh bone.


Published by: Therapeutic Pillow