Do you use your thumbs a lot when you massage someone?
You can hurt the base of your thumbs easily if you depend on your thumbs to do all the work especially in open thumb position.
Use a hooked thumb instead.
You can use it to press the acupressure points, circle on knots, even glide up the area between the shoulder blade and spine where people hold lots of tension. A hooked thumb gives you more power and protects the base of the thumb. It is ideal for non-flat areas where you can grab the other side with the other fingers. If you have a long nail on your thumb, forget this technique.