A 20-year-old man, fisherman, with no medical history of interest, presented with pain and swelling in the index finger of 2 days' evolution, following puncture with a fish bone. Examination revealed the four Kanavel signs (symmetrical swelling and semi-flexion of the finger, pain on palpation over the flexor tendon path of the second finger and pain on passive extension of the finger.
Ultrasonography revealed a hypoechogenic area around the flexor tendon of the index finger and marked synovial hypervascularisation. On surgical exploration, a small amount of pus was evacuated into the synovial sheath by drainage with opening of the A1 and A5 pulleys and irrigation system.

