When orthopedic researchers measured the actual forces inside the thumb during everyday activities, they discovered something remarkable:
Every time you pinch, grip, or grasp something, the joint at the base of your thumb experiences up to 13 times the force you apply at your fingertip.
This happens because of how your thumb is built. Unlike your other fingers, your thumb's base joint (called the CMC joint) is shaped like a saddle.
This design gives you incredible dexterity—you can oppose your thumb to any finger, rotate it, and make precise movements.
But there's a tradeoff: this joint relies almost entirely on soft tissue—ligaments and muscles—to stay stable. There's no bony "socket" holding it in place like your hip or shoulder.
Over time, the ligaments supporting this high-stress joint can weaken. When that happens, every jar lid, every doorknob, every button you fasten puts tremendous strain on an increasingly vulnerable joint.
And here's what most people don't realize: you don't have to live with it.