Myofascial pain syndrome is a painful condition that affects the muscles and fascia, the sheath of tissue that surrounds the muscles. Myofascial pain syndrome differs from other types of pain conditions in that the pain originates in trigger points, sensitive points in the muscles that trigger sensations of pain when touched.
Trigger points can be latent or active. A latent trigger point does not cause constant pain, but is tender when touched and can be activated through muscle use. An active trigger point causes constant pain and can prevent normal muscle functioning, leading to decreased range of motion and weakness.