Damage to underling tissues can occur, however, under some circumstances. Let us say, for example, that the practitioner applies ultrasound to a body area where very little muscle, connective tissue, and fat separate the skin from the underlying bone. And let's say that the patient doesn't withdraw quickly enough from the sound head. (This is likely only with a patient whose sensory nerves in the area are damaged before the treatment and don't normally conduct heat signals into the spinal cord and brain. Sensory nerves, for example, don't function normally in some extremely old and physiologically decayed people.) When the patient doesn’t withdraw quickly enough from the sound head, the ultrasound energy could—at least theoretically—cause a cavity to form under the membrane (called the "periosteum") that covers and adheres to bone. This "cavitation," as we call it, under the periosteum, would be extremely painful. I don't believe cavitation of the periosteum occurs very often. As I said, the heat build up at the skin during excess ultrasound exposure causes most patients to reflexly withdrawal from the sound head. This withdrawal reflex usually protects against damage beneath the skin.

A more likely cause of your continuing pain after the ultrasound treatment is activation of one or more trigger points. Ultrasound energy is a mechanical force. An excess of this mechanical force is somewhat akin to someone applying tremendous pressure to an inactive trigger point with a finger or the point of the elbow. The pressure would irritate the trigger point and cause it to refer pain. The trigger point might be housed in the underlying myofascia (muscle and its connective tissues) or some tendon, ligament, or the periosteal membrane.

A practitioner skilled at locating trigger points can usually to determine during one exam whether your pain is caused by a trigger point. Unfortunately, a problem today is finding a practitioner who is properly trained and skilled at locating trigger points. Some massage therapist, physical therapists, and physicians (either medical, osteopathic, chiropractic, or naturopathic) are highly skilled at doing trigger point exams. In my experience, however, most are not—although many mistakenly believe they are. Also unfortunate is another fact: Many board certified pain management specialists aren’t able to competently do a trigger point exam. If a certified myofascial trigger point therapist lives in your area, he or she is almost certain to do an examination properly. These therapists are by far your best bet for getting a proper exam.