Signs and symptoms of myofascial pain syndrome may include:

• Deep, aching pain in a muscle
• Pain that persists or worsens
• A tender knot in a muscle
• Difficulty sleeping due to pain

Sensitive areas of tight muscle fibers can form in your muscles after injuries or overuse. These sensitive areas are called trigger points. A trigger point in a muscle can cause strain and pain throughout the muscle. When this pain persists and worsens, doctors call it myofascial pain syndrome.

Myofascial pain syndrome is caused by a stimulus, such as muscle tightness, that sets off trigger points in your muscles. Factors that may increase your risk of muscle trigger points include:

• Muscle injury. An acute muscle injury or continual muscle stress may lead to the development of trigger points. For example, a spot within or near a strained muscle may become a trigger point. Repetitive motions and poor posture also may increase your risk.
• Stress and anxiety. People who frequently experience stress and anxiety may be more likely to develop trigger points in their muscles. One theory holds that these people may be more likely to clench their muscles, a form of repeated strain that leaves muscles susceptible to trigger points.

Complications associated with myofascial pain syndrome may include:

• Sleep problems. Signs and symptoms of myofascial pain syndrome may make it difficult to sleep at night. You may have trouble finding a comfortable sleep position. And if you move at night, you might hit a trigger point and awaken.
• Fibromyalgia. Some research suggests that myofascial pain syndrome may develop into fibromyalgia in some people. Fibromyalgia is a chronic condition that features widespread pain. It's believed that the brains of people with fibromyalgia become more sensitive to pain signals over time. Some doctors believe myofascial pain syndrome may play a role in starting this process.