Boxer knuckle (not to be confused with a Boxer fracture) refers to an appearance when there is a disruption to the sagittal bands of the extensor hood, particularly over the metacarpophalangeal (MCP) joint.
It often tends to result when a clench fisted hand strikes an object in a traumatic situation. Less often it can also result in a non traumatic situation such in the case of an inflammatory arthritis (e.g rheumatoid arthritis).
The ulnar and radial sagittal bands exert tensile forces in opposite directions during flexion, which keeps the extensor tendon in apposition with the metacarpal bone.
It is thought that the long finger is the most commonly affected.
May show radial or ulnar subluxation/dislocation of the extensor tendons from its usual position 3. This can be better elicited on dynamic sonography.
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- 3. Lopez-ben R, Lee DH, Nicolodi DJ. Boxer knuckle (injury of the extensor hood with extensor tendon subluxation): diagnosis with dynamic US--report of three cases. Radiology. 2003;228 (3): 642-6. doi:10.1148/radiol.2283020833 - Pubmed citation