Carpal tunnel syndrome occurs when a combination of health conditions and activities puts pressure on the median nerve as it passes through the carpal tunnel in your wrist. This pressure leads to tingling, numbness, pain, and/or weakness in parts of your hand and, sometimes, up into your arm. Anything that decreases the amount of space in the carpal tunnel, increases the amount of tissue in the tunnel, or increases the sensitivity of the median nerve can lead to Carpal Tunnel Syndrome.

Factors that help cause Carpal Tunnel Syndrome include:

• Conditions or illnesses that can cause or contribute to arm pain or swelling in the joints and soft tissues in the arm, or to reduced blood flow to the hands. These conditions and illnesses include obesity, rheumatoid arthritis, gout, diabetes, lupus, or hypothyroidism.
• Repeated hand and wrist movements that cause the membranes surrounding the tendons (tendon sheaths) to swell (tenosynovitis).
• Buildup of fluid (edema) in the carpal tunnel that can occur from pregnancy or such conditions as rheumatoid arthritis or diabetes.
• Broken wrist bones, dislocated bones, new bone growth from healing bones, or bone spurs. These can take up space in the carpal tunnel and put more pressure on the median nerve.
• Tumors and other growths (such as ganglions). These uncommon causes of carpal tunnel syndrome are usually benign.
• Normal wear and tear of the tissues in the hand and wrist caused by aging and repeated movements of the hand or wrist.
• Smoking, which may contribute to Carpal Tunnel Syndrome by affecting the blood flow to the median nerve.

Carpal tunnel syndrome is a common work-related injury. Work that requires forceful or repetitive hand movements, hand-arm vibration, or working for long periods in the same or in awkward positions-usually when combined with underlying health conditions-may cause Carpal Tunnel Syndrome.¹

In some cases the cause of Carpal Tunnel Syndrome cannot be determined.