IMPORTANT: We currently have a number of bugs related to image cropping and are actively trying to resolve them. In the meantime, we have disabled cropping. Apologies for any inconvenience. Stay informed: radiopaedia.org/chat

Boxer knuckle (ultrasound)

Case contributed by Maulik S Patel
Diagnosis almost certain

Presentation

Left third MCP region pain. The dorsal side swelling with tendon snapping.

Patient Data

Age: 75
Gender: Female
ultrasound

Intact extensor tendon of the middle finger. Short-axis image with MCP extension shows ulnar side subluxation of the 3rd finger extensor tendon. The tendon dislocates with MCP flexion. The radial side sagittal band is not seen.

The first two short-axis cine-loops run from the proximal to the distal direction. During MCP flexion to extension movement, the third cine-loop shows tendon snapping/ tendon relocating.

4th finger extensor tendon and sagittal bands are normal without tendon subluxation/ dislocation.

Case Discussion

The patient tried to get up supporting the left hand on the ground. It resulted in the sudden onset of pain involving the middle finger MCP region. It was followed by dorsal side swelling and snapping with finger extension.

The ultrasound findings favor radial side sagittal band injury with ulnar side tendon subluxation/ dislocation. The tendon relocation with finger extension results in snapping.

How to use cases

You can use Radiopaedia cases in a variety of ways to help you learn and teach.

Creating your own cases is easy.

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.