The inability to fully straighten a sprained finger is often due to the injury of a specific ligament within the finger joint.
The Volar Plate and Finger Extension
When you sprain your finger, you are likely to injure one or more of the ligaments supporting the joint. The ligament that is injured most often is called the volar plate (palmar plate). This crucial ligament is located on the palm side of your finger, and its primary job is to prevent the joint from over-extending. In other words, it prevents the finger from bending too far backwards.
How a Sprain Affects Extension
When the volar plate is injured during a sprain, it can become:
- Swollen: The area around the ligament may swell with inflammation, limiting the range of motion.
- Painful: The injured ligament causes pain, making it difficult and uncomfortable to attempt to straighten the finger.
- Stiff: The inflammatory response can lead to stiffness, further restricting the finger's ability to extend fully.
Understanding the Limitation
Because the volar plate is crucial in preventing hyperextension (over straightening), it can't do its job effectively after it is injured. As the volar plate heals, scar tissue may form, which can further limit the finger's range of motion, preventing full extension and leading to difficulty straightening your finger.
Summary:
Here is a table summarising why you can't straighten a sprained finger:
| Issue | Explanation |
|---|---|
| Volar Plate Injury | The volar plate (palmar plate), which prevents hyperextension, is often injured in a finger sprain. |
| Swelling and Pain | Inflammation and pain make it difficult to move the finger normally. |
| Stiffness | The injured area can become stiff, limiting movement. |
| Scar Tissue | As the injury heals, scar tissue can further hinder the finger's range of motion. |
In short, the injury of the volar plate, along with swelling, pain, and possible scar tissue formation, contributes to the inability to fully straighten a sprained finger.
