Muscle (myofascial) pain

Literally pain from muscle, but usually in the chronic form is a result of repetitive stress injuries, such as poor ergonomics at a place of work causing neck pain.
Overuse of muscles leads to buildup of toxins in local areas of the muscle that cause pain. Treatment usually is at identifying and correcting the problem but return to function without pain often is accomplished with stretching, physical therapy, medications and injection techniques.