A torn thumb ligament is a very serious injury. If the ligament is completely torn, it can cause the thumb to become completely dislocated. This can be extremely painful and may require surgery to fix. A torn ligament can also make it difficult to move the thumb, which may make it difficult to do everyday tasks such as opening a door or using a computer. If you have a torn thumb ligament, it is important to see a doctor as soon as possible so that he or she can determine the best course of treatment.