case_images: PMC7852405_01
case_images: Sagittal MRI slice (T1 fat suppression) of the left knee showed massive synovitis where the thorn fragment was located.
case_images: jbji-6-51-g01.jpg
case_images: PMC7852405_01_jbji-6-51-g01.jpg
case_images: Ch1.F1
case_images: A second MRI showed persistent massive synovitis and accumulation of fluid, especially posteriorly (Fig. 1).
case_images: Thorn fragment (4.5 mm) removed during arthrotomy from the suprapatellar pouch.
case_images: jbji-6-51-g02.jpg
case_images: PMC7852405_01_jbji-6-51-g02.jpg
case_images: Ch1.F2
case_images: After completing the dorsal approach and opening the front of the knee, a 4.5 mm thorn fragment was found in the area of synovitis within the suprapatellar pouch (Fig. 2).
case_images: Robinia pseudoacacia, commonly
  known as black locust, populated with Pantoea agglomerans. Picture from place of accident near Zurich, Switzerland.
case_images: jbji-6-51-g03.jpg
case_images: PMC7852405_01_jbji-6-51-g03.jpg
case_images: Ch1.F3
case_images: The thorns belonged to a plant known as Robinia pseudoacacia, a widespread neophytic hardwood tree, commonly known as black locust (Fig. 3).