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What Are the Causes of MCP Hyperextension?

The metacarpophalangeal (MCP) joint is more commonly known as the knuckle. The MCP joint allows you to fine-tune your finger movements and to do things like knit, type and play musical instruments.



Hyperextension of a joint occurs when the joint is overstretched in one direction. There are a number of ways this can accidentally happen in an MCP joint.

  1. Hyperextension

    • Hyperextension occurs when a joint is bent in the direction opposite from its normal movement. This is the opposite of flexion, when a joint works in the direction it is meant to go. You are using your finger's flexion ability when you point toward your inner wrist; when you try to point toward your outer wrist, you are hyperextending.

      Your MCP does have some degree of safe hyperextension---it can go to around a 30-degree angle without injury. More than this, however, and you risk dislocation.

    Sports

    • The most common form of MCP hyperextension is in sports, as most sports involve the hand in one way or another and all of them involve moving very quickly around people and objects. For example, someone can hyperextend her finger if she receives a basketball that is coming at high speed without preparing her fingers for the impact. Alternatively, a skier can hyperextend his finger by running into a tree with an outstretched hand.

    Everyday Life

    • Opportunities to hyperextend your MCP exist everywhere. Falling over and breaking your fall with your hand is one way to do so, as is getting it caught in a door. Luckily, these injuries are generally easy to fix with time or buddy tape, which compensates for their ubiquity.

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