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By Ben Benjamin, PhD

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A Common MT Injury: You Guessed it ... Thumbs

In massage and bodywork the thumb is an important but often overused part of the body. Manual therapists are susceptible to many different thumb injuries, which often make them ponder the decision to leave the profession, or not. In the thumb alone a therapist can injure three joints, roughly seven muscles and tendons, and four primary ligaments in addition to joint dislocations.

The thumb is an extremely versatile part of the body and the most unique finger in the hand. It can flex to help you grasp a muscle, extend to hitchhike a ride, abduct to help you play the piano, and adduct to help you turn the steering wheel in your car. It can even move in a circular motion, referred to as circumduction.

The opposability of the thumb is one of the key distinguishing features of human anatomy. Our ability to simultaneously flex, abduct, and medially rotate the thumb allows us to bring the thumb tip into opposition with each of the fingertips. This provides a substantial evolutionary advantage, driving our ability to effectively use tools and manipulate small objects.

A Common MT Injury: You Guessed it ... Thumbs - Copyright – Stock Photo / Register Mark Anatomy

There are three separate joints in the thumb: the carpometacarpal (or CMC) joint, the metacarpophalangeal (or MP) joint, and the most distal, the interphalangeal (or IP) joint. All these names can make your head spin, but they're easy to understand once you break them down into their component parts. The word carpo means wrist, and metacarpal means hand bone, so the carpometacarpal (or CMC) joint is the junction of a hand bone with a wrist bone. Specifically, it's the trapezium bone of the hand that articulates with the thumb metacarpal. For this reason, the CMC joint is also often referred to as the first trapezio-metacarpal joint.

A Common MT Injury: You Guessed it ... Thumbs - Copyright – Stock Photo / Register Mark CMC Joint

The carpometacarpal joint is the most frequently injured joint in the thumb and fingers. When too much stress is placed on the thumb, the CMC joint is the first to give way and become inflamed and painful. This is particularly troublesome for massage therapists and body workers, because using the thumb has become so crucial to this kind of work. Special care must be taken by all therapists to use the thumb judiciously and correctly but use the other fingers equally and not have too much reliance on the thumb.

Unfortunately, this is especially true for therapists who are naturally very flexible. The more flexible you are the more vulnerable you are to injury. These individuals have ligaments that are longer than they should be and therefore can do all sorts of things that put them in danger. Ligaments should be tight to stabilize the joints. When they over flex and over extend they can easily become injured.   This joint is also often injured in pianists and drummers as well as the elderly who don't know how to care for their thumb and finger joints.

A Common MT Injury: You Guessed it ... Thumbs - Copyright – Stock Photo / Register Mark MP Joint

Next comes the middle joint of the thumb — the metacarpophalangeal, or MP joint. Again, metacarpo — means hand bone, and phalangeal means finger bone. So the MP joint is where the hand bone meets the finger bone. It can move through almost 90 degrees of motion in flexion but almost nothing in extension. This is the second most injured joint of the thumb. This occurs particularly through pressure techniques, squeezing actions or gripping motions.

By pressure techniques I'm referring to a movement or manipulation that applies pressure through the joint while it is held straight in extension. This puts a huge amount of stress through this joint especially for those individuals who are naturally quite flexible. This is also the joint that usually gets jammed when you bump into something with your thumb. The thumb is usually forced into over-flexion and the joint becomes irritated and inflamed.

Ip Joint

Finally, we have the interphalangeal or IP joint, the meeting of two finger bones. This is the most distal joint of the thumb, and also tends to get injured when we jam the thumb into something (usually in extension) or grip with our fingers and thumb for long periods of time throughout the day.

Editor's Note: The next article in this two-part series will cover how to assess thumb joint injuries.

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