Characterization of the Ligamentum Mucosum in the Feline and Canine Stifle

In humans, the ligamentum mucosum (LM) is described as a ligamentous structure originating from the femoral intercondylar notch and inserting into the infrapatellar fat pad. Proposed clinical implications include knee stabilization, contribution to post-operative revascularization of adjacent structures, and causation of anterior knee pain if inflamed. Published reports of the LM are rare in dogs and, to our knowledge, none exist for cats. Because common veterinary gross anatomy texts omit the LM from their descriptive anatomy of the stifle, students sometimes mistake the LM for the cranial cruciate ligament. Therefore, a description of the LM in the feline and canine stifle would serve as an important veterinary anatomy learning resource. The aim of this project was to characterize the LM in the cat and dog. Stifles were dissected from 62 cat hindlimbs (n = 24 preserved, n = 38 fresh) and 47 dog hindlimbs (n = 9 preserved, n = 38 fresh). The presence or absence of the LM was determined and described. Representative samples were processed for haematoxylin and eosin staining. Grossly, the LM was found bilaterally in 95.2% of cats and in 83.0% of canine limbs, appearing as an elastic, friable band of white-to-pink tissue tethering the infrapatellar fat pad to the femoral intercondylar notch. Histological samples revealed collagen fibrils, vascular structures and neural tissue. These data provide evidence of the LM in the cat and dog, and bolster currently available anatomic educational resources. The presence of the LM in the canine and feline stifle merits further investigation into its function in health and disease states.