The intercondylar fossa of the normal canine stifle an anatomic and radiographic study

The intercondylar fossa (ICF) in dogs consists of a cranial outlet, intercondylar shelf, caudal arch, caudal outlet, a medial wall, and a lateral wall. The normal cranial outlet is bell-shape and, in mixed-breed dogs (mean body weight 19.2 kg, N = 21), measured 5.8 mm cranially, 8.1 mm centrally, and 10.3 mm caudally. The ICF is oriented 12 degrees from the dorsal plane of the femoral diaphysis and obliqued 7 degrees, proximolateral to distomedial, in the sagittal plane. To adjust for dog size, a fossa width index (FWI) was calculated by dividing the cranial outlet width by the distance between epicondyles. The normal FWI as determined in this study was 0.18 cranially, 0.25 centrally, and 0.32 caudally. The fossa height index 0.31. Contact between the ICF and the cranial cruciate ligament began at about 115 degrees of extension. The contact area moved cranially in the intercondylar fossa as the stifle was extended. Evaluation of the ICF can be performed radiographically but positioning is critical.