Muscle sprains and strains are among the most common causes of back pain. A number of factors can cause these, including injury, improperly lifting heavy objects, twisting sharply or merely standing for long periods of time.

A person’s back is composed of the bones, muscles and other tissues that form the posterior part of the trunk, which runs from the neck to the pelvis. The back is held upright by muscles and ligaments that are attached to the bones of the back. These bones, called vertebrae, are stacked on top of one another. Together, these bones are known as the spine, spinal column or vertebral column.

The back is vulnerable to injury because it supports most of the body’s weight. Nearly four in five people suffer from back pain at some point in their lives, according to the National Institutes of Health. In some cases, back pain is the result of a herniated disc or other damage to the intervertebral discs that cushion and separate the individual vertebrae that make up the spine.

However, in many cases, back pain is the result of a sprain or strain. A sprain is a stretching or tearing of ligaments, the tough, fibrous tissue that connects one bone to another. A strain is a stretching or tearing of a muscle, which can occur if a muscle suddenly contracts or is stretched too far. Strains are commonly referred to as “pulled muscles.”

Commonly injured muscles of the back include:

• Erector spinae. Firm, prominent muscles in the lower back on either side of the midline. They can become painful when they are tensed or cramped up in spasms.
  
  
• Psoas minor. A muscle of the abdomen that flexes the trunk. Strain on this muscle creates tremendous force on the lumbar spine of the lower part of the back, which can be very painful.

Most people who suffer a back sprain or strain have a good prognosis, only occasionally accompanied by minor scar tissue.