What is Repetitive Strain Injury (RSI) and Carpal Tunnel Syndrome (CTS)

On this Page: What is RSI of the hand? Who is at risk? Some Numbers What causes RSI? What causes CTS?

What is Repetitive Strain Injury (RSI) of the Hand?

RSI is a general term for disorders that occur from prolonged, repetitious use of the hands which results in pain, burning, swelling, tingling, numbness, loss of dexterity and weakness. Other synonyms for RSI include: Cumulative Trauma Disorder (CTD), Occupational Overuse Syndrome (OOS) and Repetitive Motion Syndrome (RMS). The more specific disorders are Carpal Tunnel Syndrome (CTS), Tendonitis, Tenosynovitis and a host of others. Of course CTS is the most common malady brought on by repetitive hand motion.

Who is at Risk?

Those at risk include: computer users, assembly-line workers, stock clerks, warehouse workers, drivers, transcriptionists, garment workers, athletes, meat and poultry processors, painters, writers, gardeners, golfers, carpenters, bank tellers, data entry clerks, accountants, bricklayers, secretaries, construction workers, CAD and graphic designers, programmers, silkscreeners, artists, needlepoint hobbyists, draftsmen, gardeners, crafts enthusiasts, sportsmen, musicians, knitters, crocheters, checkout clerks and anyone else who uses their hands continually or forcefully. In addition, pregnant women and certain other conditions, have a higher risk due to fluid retention.

Some Quick Numbers

By some estimates, about 27 million people have visited a medical professional for RSI of the hand and, perhaps, another 40 million have experienced symptoms but did not seek professional help. According to the Bureau of Labor Statistics, RSI's of all types account for 60% of all reported occupational illnesses. The estimated direct cost to businesses was over $25 billion in 1993 just in the U.S. The National Center for Health Statistics reported that 849,000 new problem visits were made to physicians in office-based practices in 1994 due to CTS and carpal tunnel release operations are the second most common work related surgical procedure in the U.S. OSHA shows CTS as having the highest median days away from work, greater than fractures or even amputations. A CTDNews survey revealed that CTS is the costliest Cumulative Trauma Disorder, with back injuries second. However, after factoring in not only lost days and medical expenses (which alone can reach $29,000) but also temporary help and overall lost productivity, the overall cost could reach a whopping $60,000+ per incident. Finally, the National Institute of Occupational Safety and Health (NIOSH) has predicted that 50% of the work force will suffer from RSIs (of all kinds) by the year 2000.

Although surgery is a common treatment when CTS symptoms become unbearable, it is often not a cure, especially if the patient returns to the type of work that brought it on in the first place. One study showed 57% of patients reported a return of some symptoms. In addition, it has been estimated that only 23% of CTS patients were able to return to their previous jobs after surgery and perhaps a third of CTS patients will require unlimited medical treatment. Prevention, in this case, is the best medicine. Remember, poor ergonomics and posture contribute to RSI as well.

What causes RSI of the hand? (a brief explanation)

According to the Occupational Safety And Health Service of New Zealand, restricted blood flow is often the culprit. Lack of blood to the muscles, tendons and nerves can cause or aggravate a host of conditions, even, perhaps, arthritis. When you tense a muscle to just 50% of its ability, the blood flowing through the capillaries in the muscle can be completely shut off. (Tensed muscle fibers pressure the capillaries thereby restricting the blood flow.) As the muscle is continually tensed and no fresh blood is supplied, it switches from aerobic (with oxygen) to anaerobic (without oxygen) metabolism. This produces by-products such as lactic acid which can build up and cause cell damage and pain. Subsequently, the neighboring muscles work harder to help carry the load, but because they are not designed to do the job as efficiently, those muscles fatigue (anaerobic) even faster. Muscle tension, therefore, restricts blood flow and restricted blood flow causes more tension in other muscles. If the muscles are not allowed to relax, cellular degeneration can rapidly increase as a vicious cycle takes hold. The tensed muscles also pressure surrounding nerves which causes tingling, numbness, and more subsequent injury. In addition, the lack of blood increases the likelihood of degeneration and inflammation throughout the system and, of course, retards healing. And though the cycle may stop when you rest your hands, by the time you feel any symptoms, the damage has already started. Consequently, it will take less stress to bring on symptoms in the future.

Repeated tensing of the hand can cause the fibers of the tendons running through the carpal tunnel to separate or break. This causes friction between the tendon and it's sheath (tenosynovium) and ultimately tendonitis. Tenosynovitis occurs when the sheath cannot properly lubricate the tendon it surrounds due the the repetitive hand movement and the sheath itself becomes inflamed. Tightly gripping something for too long and forceful movements can lead to problems as well.

The best known consequence of RSI of the hand is, of course, Carpal Tunnel Syndrome.

What Causes Carpal Tunnel Syndrome (CTS)?

As shown, the Carpal Tunnel (pink area) is made up of several bones (white) connected by ligaments. The largest of which is the Transverse Carpal Ligament (blue). These structures form the perimeter of a passage through it's center called the carpal tunnel (also called the carpal canal). Through this tunnel run nerves, tendons, blood and other soft tissues. For a variety of reasons some of these soft tissues swell, especially the tendons (red) and the protective sheaths that cover them. Overuse (RSI), injury, friction, fractures, fluid retention, forceful movements and infection are a few of the more common causes. However, unlike most of your body where swelling simply protrudes, this swelling has no place to expand since it is encircled by bones and ligaments. Consequently, because the swelling is contained, pressure builds in the tunnel. This pressure (also called compression) then crushes the main nerve to your hand called the Median Nerve (yellow), causing it not to function properly. The pressure also obstructs blood flow which retards healing and causes further cell degeneration. The usual symptoms are: Fatigue, Pain, Weakness, Loss of Dexterity, Stiffness, Cramping, Numbness, Cold, Burning or Tingling. These symptoms also strike while resting. Frequently the pain is located in the Thenar muscle, at the base of the thumb. In very advanced cases this muscle may atrophy and become useless as it is deprived of stimulation by pressure on the Median Nerve.

A common test for CTS is Phalen's Maneuver. Put the backs of your hands together while keeping your arms parallel to the floor and your fingers pointing down. Hold your hands together firmly. If within a minute, you experience one, or a combination, of the symptoms, you probably have the disorder. Don't hold this position for more than the required minute.

Although many more theories abound as to the exact causes of RSIs and CTS in particular, it is a fact that, for many people, it doesn't take years of strain to cause it. Just a few instances of overuse or ignoring a mild condition for too long, may be enough to push it to an acute stage. When you feel any of the symptoms, the cycle could be starting and it is important that you take action quickly.. Also see our Tips page for info on other ways to reduce the chances of contracting Repetitive Strain Injuries. Click here for NIOSH's CTS Page.

If you find that preventative measures aren't helping, see a doctor or therapist as soon as possible. Prompt attention can mean the difference between a quick recovery and a lifetime of suffering. And, by all means, be sure the physician you choose is familiar with these disorders.

Glossary of Terms

Median Nerve: a major nerve to the hand that controls the thumb, index and ring finger
Carpal Tunnel: a passage in the wrist through which the median nerve and tendons travel to the hand, much of it located at the base of the palm
Transverse Carpal Ligament: a tough but elastic structure which holds the bones of the Carpal Tunnel together, often surgically cut to relieve pressure on the median nerve
Repetitive Strain Injuries (RSI), Cumulative Trauma Disorder (CTD), Repetitive Motion Syndrome (RMS), Occupational Overuse Syndrome (OOS): synonymous terms for disorders caused by prolonged, repetitious tasks
Carpal Tunnel Syndrome (CTS): pressure (or compression) on the median nerve that may cause pain, numbness, weakness, etc.
Tendonitis: inflammation of a tendon, the structures that link muscles to bones
Tenosynovitis: inflammation of a tendon's sheath which causes it to swell and may also retard proper lubrication of the tendon inducing more injury
Carpal Canal: sometimes used interchangeably with Carpal Tunnel
Ulnar Nerve: another main nerve to the hand which controls the last two fingers, it passes outside the carpal tunnel but can be affected by tennis elbow or displacement