My thumb hurts in the joint! Many patients want to use the right technical terms when talking with their physician, and this can certainly improve the efficiency of your office visit. In this article, I’ll quickly show you how to identify the joints in your thumb.
In this series of articles, I’ll go through some of these terms along with some helpful diagrams and shed some light on the common language of hand and arm surgery.
Three Joints of the Thumb
The three joints are as follows:
- Carpometacarpal (CMC) Joint
- Metacarpophalangeal (MP) Joint
- Interphalangeal (IP) Joint
The CMC joint of the thumb is located at the junction point of the thumb and the wrist. Break down the words in the name, carpometacarpal, and you get carpo- (wrist) and metacarpal (hand bone). This joint is commonly affected by arthritis.
The CMC joint’s main function is to allow the thumb to open and grasp wide objects, like a basketball or (for us mortals) a large glass of your favorite beverage.
The MP joint of the thumb is the middle joint of the thumb, located between the CMC joint and the tip of the thumb. Break down the words in the name, metacarpophalangeal, and you get metacarpo- (hand bone) and phalangeal (finger bone). This joint moves a lot in some people and just a little in other people. Compare MP thumb joints around your family and you may find some big differences.
Sometimes this joint is injured when you jam it in a skiing or sports injury. This causes the joint to pop out of place and tear a ligament. This is sometimes called skiier’s thumb. The ligament can heal without surgery if it’s not moved out of place.
The IP joint of the thumb is at the tip of the thumb. The word interphalangeal means “between the phalanges”. Important tendons attach on the bottom and top of this joint and move the tip of your thumb back and forth.
If you jam your thumb and the tip of the thumb doesn’t move normally, this could be a sign of a ruptured or torn tendon. Tendons move joints – when a tendon is ripped off the bone, the joint no longer moves normally.
Familiarity with the language of the joints of the thumb will help streamline your visit with a hand specialist or other health care provider.