Sore trigger point areas develop from chronic conditions such as from injuries , fibromyalgia , or repetitive stress causing ongoing spasms that become chronic and never fully let up not allowing the muscle to ever relax . This can happen to any muscle in the body at any age . Females tend to make up a significant portion of patients . The lower back and pelvic region is commonly affected as a point of significant weight bearing . A local anesthetic is used for the trigger point injections so that they are essentially not painful and generally offer complete immediate pain relief in the region injected .