Hyperechoic nodule adjacent to the finger’s collateral ligament

[Xue Heng]

This is a 49-year-old female who was found to have a mass on the radial side of the proximal interphalangeal joint of the fourth finger, with mild tenderness. Ultrasound reveals a hyperechoic lesion adjacent to the radial collateral ligament. Dear Steve, I would like to ask for your opinion on the possible diagnosis and its underlying cause. Thank you for your time and expertise.

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[Stephen Bird]

Hi Xue,

I have a few options for you.

It looks like a crystal deposition into the joint capsule (RCL) of the PIP joint.

The joint capsule has an enthesis and hence hydroxyapatite is a possibility.
CPPD is also a possibility, but I think less likely as the crystals look cloud like typical of hydroxyapatite.
Gout is another option.
If it is hydroxyapatite or CPPD I would expect to see some evidence of it on a PD radiograph.
If it is gout i think it will e invisible on the radiograph.

Another alternative is some granulation tissue following trauma to the RCL.

They are my options,

Steve.

[Xue Heng]

Thank you so much for your thoughtful and detailed response — I truly appreciate you taking the time to share your expertise.

I find your differential diagnosis very helpful, especially the distinction between hydroxyapatite, CPPD, and gout based on the sonographic appearance and expected radiographic findings. The idea of granulation tissue following trauma is also an important consideration that I’ll be sure to keep in mind.

Thanks again for your guidance — always a pleasure learning from you.

[Author]

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