What is the cause of inflexibility in both hands? The most common causes of inflexibility are as follows: the first and most common is Parkinson’s disease, which is characterized by stiffness, slow movements, tremors and abnormal gait. This requires a visit to the neurology department of the hospital for a clear diagnosis. The second cause is cerebrovascular disease, especially multiple cerebral infarcts and atherosclerosis, which can lead to decreased flexibility and skill of hand movement. The third factor is some rheumatic bone and joint diseases, which can also lead to inflexible movement of both hands.