Carpal tunnel syndrome (CTS) is a progressively painful condition. It often results from a combination of factors that increase pressure on the median nerve (which help controls sensations and movement in the hand and fingers) and tendons in the carpal tunnel (tunnel-like structure of bones and ligaments in the wrist), rather than a problem with the nerve itself.  

In most cases, the exact cause of CTS is unknown. However, several risk factors have been associated with the disorder, including:

• Heredity. Recent studies have strengthened scientists' belief that genetic predisposition plays a role in CTS.
  
  
• Injury or trauma. A fracture or sprain of the wrist can cause swelling and pressure on the median nerve, increasing the risk of CTS. Forceful and stressful movements of the hand and wrist, such as those associated with the use of heavy machinery or power tools, can also cause trauma.
  
  
• Repetitive hand, wrist or finger movement. People who repeatedly perform the same hand-intensive movements for a prolonged period might be more likely to develop CTS. Such movements may involve a combination of awkward, repetitive wrist or finger motions, forceful pinching or gripping and working with vibrating tools.
  
  However, the association between activities such as typing and CTS remains unclear. Some research suggests there may be a link, but other studies have found no higher prevalence of CTS in some professions that strain the hands, such as court reporting and construction work.

• Improper posture and ergonomics. Poor positioning of the wrist or hands during repetitive activities may increase the risk of CTS.
  
  
• Sex and age. Women are three times more likely than men to develop CTS. In women, the incidence peaks after menopause. For men, the risk increases during middle age.
  
  
• Pregnancy. The buildup of fluid (edema) in the carpal tunnel that occurs during pregnancy may put pregnant women at risk for developing CTS. However, in most cases, CTS resolves after childbirth.
  
  
• Menopause. Although the link between the loss of ovarian function and CTS is unclear, studies suggest that hormonal changes occurring during menopause may put women at risk for CTS. In addition, sometimes the wrist structures of postmenopausal women become enlarged and can press on the median nerve and induce symptoms of CTS.
  
  
• Mastectomy (surgical removal of a breast, usually performed to treat breast cancer). Some women who undergo this procedure experience lymphedema (excessive buildup of fluids in the lymph nodes and vessels). In mastectomy patients, lymphedema is painful and may cause the arm to swell. In rare cases, some of these patients may develop CTS because of pressure on the median nerve from the swelling.
  
  
• Size of the carpal tunnel. Studies suggest that the cross-sectional area of the carpal tunnel may be narrower in CTS patients.
  
  
• Obesity. Research suggests an increased risk of CTS in individuals with a body mass index (BMI) greater than 29.
  
  
• Kidney dialysis (use of a machine or other method to filter wastes from the blood). CTS is common in patients with kidney disease who undergo prolonged dialysis treatment. CTS is present in as many as 30 percent of patients who undergo dialysis for more than nine years.
  
  
• Growth hormone treatments. Some endocrine disorders are treatment with growth hormone, which is also sometimes promoted as an anti-aging treatment despite negative side effects including joint swelling, CTS and increased risk of diabetes.
  
  

A higher incidence of CTS has been noted in patients who have one or more of a wide range of diseases, including:

• Rheumatoid arthritis (RA). A debilitating inflammatory disease that causes pain, swelling, stiffness and loss of function in the joints. RA patients may be at higher risk for developing CTS. However, in many cases, the symptoms of median nerve compression resolve as the rheumatoid arthritis is treated.
  
  
• Gout. A form of arthritis caused by the buildup of uric acid crystals in the joints, causing inflammation, swelling and pain. The joint swelling in gout patients may predispose them to CTS.
  
  
• Osteoarthritis. The most common form of arthritis, which can affect the wrist.
  
  
• Lupus. An inflammatory autoimmune disorder that can affect the skin, joints and internal organs. The joint inflammation associated with lupus may put patients at an increased risk for developing CTS.
  
  
• Acromegaly. A rare endocrine disorder in which the pituitary gland produces excess growth hormone. Patients experience overgrowth of bone and cartilage, which can lead to CTS. In most cases, treatment for acromegaly usually leads to rapid resolution of CTS.
  
  
• Diabetes. Diabetic patients may be at higher risk for CTS because diabetes makes the nerves more susceptible to compression and impingement.