Patients in the intervention group will receive 12 treatments (twice a week for a period of six weeks) with the Phystrac mechanical traction device (type GR 10). The Phystrac provides mechanical traction to the wrist using weights between 1 and 18 kg. One treatment takes 10 to 15 minutes per diseased hand. The patient will be seated beside the traction device on a seat that is adjustable in height. The patient will put his arm on the arm support of the device and will be secured with two Velcro straps; one above and one below the elbow. Another Velcro strap which is attached to the weights will be fastened around the wrist with the palm of the hand upwards. The weight is set at 5 kg for women and 7 kg for men during the first treatment session. Every following treatment session, the weight is increased by 1 kg for women and 2 kg for men until 10 kg for women or 13 kg for men, or until the mechanical traction becomes painful or uncomfortable for the patient. When the patient is fitted correctly, the weight will be lowered and provides a pulling force on the wrist. After eight seconds the weight is lifted, providing a rest period of four seconds. This cycle will be repeated ten times. After 10 traction movements, the device stops and the researcher will rotate the wrist straps 30 degrees supination, after which another 10 traction movements will be provided. After that, a third set of 10 traction movements will be provided in 30 degrees pronation position. In total, 30 traction movements will be applied during each treatment. During the six weeks of treatment, patients will not receive other forms of treatment. After the six weeks of treatment, patients are allowed to receive usual CTS care when mechanical traction was not sufficient.