A 10-year-old, neutered male Labrador retriever presented with progressive left
hind lameness. Ultrasonography revealed large, subcutaneous, ovoid cysts around the stifle
joint. Radiographic and computed tomographic images revealed periosteal reaction of the
distal femur. Magnetic resonance (MR) imaging showed a large cyst that was hypointense in
T1-weighted images, hyperintense in T2-weighted images and had a thin lining that was
enhanced by intravenous gadonium injection. The cyst communicated with the joint cavity
and other small cysts around the joint. Histopathology of an excisional biopsy specimen
led to diagnosis of ganglion cyst. This report provides MR images of a ganglion cyst in a
canine stifle.