4-Year-Old FS Manx Cat

Signalment & History

A 4 year old FS Manx Cat presents with a 1 day history of left pelvic limb lameness. On physical exam the pain is localized to the stifle.

CC Left stifle Lateral left stifle


The medial fabella (of the medial tendon of origin of the gastrocnemius muscle) is unable to be visualized on these radiographs.


Non-mineralized medial fabellae do not cause clinical signs of lameness in cats; it is a normal anatomical variant. No radiographic abnormalities are detected.

  • There is a lateral fabella and a smaller medial fabella in the lateral and medial heads of the gastrocnemius muscle
  • Radiolucent medial fabellae are a common and incidental finding on feline stifle radiographs. Histologically the fabellae are comprised of fibrocartilage rather than ossified bone.
  • Non-mineralized medial fabellae are more common in domestic cats (i.e. domestic short, medium and long haired breeds) than in pedigree breeds.
  • Non-mineralized medial fabellae are not clinically significant. However, non-mineralized fabellae are unable to be assessed radiographically for disease (such as trauma).


Arnbjerg (1993) Fabellae and popliteal sesamoid bones in cats. Journal of Small Animal Practice; 34(2) 95-98.