Elbow dysplasia is an important cause of forelimb lameness in large breed dogs. The aim ofthis study was to report on the arthroscopic findings associated with medial compartment erosion(MCE) of the canine elbow joint. Retrospectively, records of 84 elbow joints from 66 dogsdiagnosed arthroscopically with MCE were retrieved from a medical records database (2008 -2012). The radiographic degree of osteoarthritis was determined. Arthroscopic images and videoswere evaluated in detail. In nine joints (10.7%), MCE was the only pathological finding (= group1). Group 2 (n = 50, 59.5%) consisted of elbows with MCE concomitant with medial coronoidprocess (MCP) pathology. In group 3 (n = 25 joints, 29.8%), MCE was diagnosed during a second-look arthroscopy in dogs presented with lameness after arthroscopic treatment for medialcoronoid disease. There was a significant age difference (p < 0.001) between the groups, with dogsin group 1 being the oldest. Complete erosion of the medial compartment was most commonlyfound in group 1, whereas focal cartilage erosion was mostly identified in group 2. Overall, additionalcartilage pathology of the lateral part of the humeral condyle and/or the radial head wasrecognized in 58.3% of the joints (49/84).