Ask the Doctors September 2006 Issue

Ask the Doctors: 09/06

I’ve been reading about pulsed-signal therapy and how it can help patients with fibromyalgia. How does it work? Is it FDA approved? Is it expensive?

Pulsed-signal therapy (PST) involves the use of a low-power electromagnetic field through which a pulsed signal is directed to the affected area to stimulate the healing process. The painful area, such as the knee or neck, is placed inside a magnetic coil, through which electric current is sent in pulses. At this time, the entire body cannot be accommodated, as might be necessary for treating fibromyalgia, and I am unaware of any studies evaluating the use of PST in the treatment of fibromyalgia.

Although PST is used extensively in Europe and Canada (where it is even included in many hotel/spa packages), there are few studies and little evidence to support its use in most musculoskeletal disorders.

Most published reports on the effectiveness of PST in treating osteoarthritis have been written by its developers. PST currently is not FDA-approved. In Canada, a course of treatment (usually nine or 10 one-hour treatments) at a PST center costs approximately $2,000.


How do you evaluate a joint with rheumatoid arthritis or osteoarthritis to determine if joint damage is getting worse? I know X-rays show some kinds of damage, but do they show soft-tissue damage as well?

X-rays can show changes indicative of disease progression, such as joint-space narrowing, bone cysts, and osteophytes (bone spurs). It can help determine if symptoms of arthritis—swelling, tenderness, loss of motion, instability—are related to the bones or the soft tissues, and the appearance of joints on X-rays is often distinctive for various forms of arthritis.

Magnetic resonance imaging (MRI) is a sensitive indicator of early rheumatoid joint destruction, but it is very expensive. Although it is not routinely used in patients with arthritis, MRI is useful when other problems—such as meniscal tears or ligament injuries—exist because it permits the simultaneous imaging of all joint components with excellent contrast between different tissues.

Computed tomography (CT) is helpful in detecting the fine details of bone, but it also is a relatively expensive test and does not give as clear a picture of the soft tissues as does evaluation by MRI.

Ultrasonography is an attractive method of imaging because of its low cost, absence of harmful radiation, and the rapidity of its imaging. Recent advances in ultrasound technology have allowed for the development of sonographic equipment for imaging inflamed joints in patients with rheumatoid arthritis.

X-rays, however, remain the least expensive and best method for monitoring progression of osteoarthritis and rheumatoid arthritis.


I have rheumatoid arthritis in my knee and have been receiving cortisone injections for several years, but I'm concerned. Is there a limit on how many injections I can safely have in a year, and how many years I can take these injections?

The American College of Rheumatology recommends no more than three to four cortisone injections per joint per year. Although no one knows what the long-term effect of this many injections over a period of several  years will be, data obtained through animal studies indicates that cartilage can be damaged by too-frequent injections. In clinical practice, when a patient continues to require three to four injections each year, joint-replacement surgery should be considered.