What has happened to this man’s finger?

This is a 48-year-old man who fell nine months ago and now has swelling and pain in the right index finger.

  1. What do the paired arrows label in image 1?
  2. What does the single arrow label in image 1?
  3. What does the single vertical arrow label in image 2?
  4. What do the sets of three paired arrows label in image 2?
  5. With image three, what do you think is the patient’s story?


  1. The paired arrows point to a torn ulnar collateral ligament in the first image.
  2. The single long arrow points to periosteal perpendicular reaction (first image).
  3. The single vertical arrow (second image) points to an inflamed irregular destructive erosion.
  4. The multiple short-axis arrows on T1 coronal imaging (second image, three paired arrows) point to extensive periosteal reaction.
  5. The most plausible explanation for what has happened to this finger is a traumatic injury leading to instability, cartilage injury and collateral ligament injury resulting in chronic indolent infection of the joint space. To back this up, see short-axis axial T2 in which arrows point to a large proteinaceous palmar effusion (short-axis T2 arrows, third image).
  6. For more case review, head to MRI Online.

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